PtAu3 cluster complexes with narrow-band emissions for solution-processed organic light emitting diodes

Article abstract of DOI:10.1039/c8tc06384b

In order to develop solution-processable organic light-emitting diodes (OLEDs) with improved optical properties, PtAu₃ heterometallic cluster complexes that exhibit narrow-band emission spectra were prepared through judicious molecular design.

Full text of DOI:10.1039/c8tc06384b

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PAPER
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Nguyên T. K. Thanh, Xiaodi Su et al.
Fine-tuning of gold nanorod dimensions and plasmonic properties using
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PtAu3 Cluster Complexes with Narrow-band Emission for Solution-
Processed Organic Light Emitting Diodes
Received 00th January 20xx,
Accepted 00th January 20xx
‡
‡
Nagarajan Natarajan, Lin-Xi Shi, Hui Xiao, Jin-Yun Wang,* Li-Yi Zhang, Xu Zhang, and Zhong-Ning
Chen*
DOI: 10.1039/x0xx00000x
In order to develop solution-processable organic light-emitting diodes (OLEDs) with improved optical properties, PtAu3
heterometallic cluster complexes that exhibit narrow-band emission spectra were prepared through a judicious molecular
design. The brightly emissive PtAu3 complexes with robust chemical and thermal stability (> 290 oC) show
photoluminescent quantum yields (PLQY) of 80.5%−90.1% in doped films. The dihedral angle between the plane of
aromatic acetylide and platinum(II) coordination square plane exerts dramatic influence on the full width at half maximum
(FWHM) of phosphorescent emission, in which the better the co-planarity, the narrower the FWHM. Theoretical studies
www.rsc.org/
3
suggest that the more involvment of acetylide-to-Pt LMCT state is in favor of attaining narrow-band emission. Solution-
processed OLEDs based on narrow-band green emitter gives a maximum current efficiency (CE) of 38.7 cd A−1, power
efficiency (PE) of 22.9 lm W− and external quantum efficiency (EQE) of 10.3% with FWHM of 42 nm and CIE (0.30, 0.61).
1
The PtAu3 cluster complex with phenanthrene-fused carbazole-acetylide displays improved device performance due to the
−
1
enhanced hole-carrier ability withthe peak CE of 62.2 cd A−1, PE of 30.3 lm W and EQE of 16.6 %. The elegant synthetic
strategy by combining electron and/or hole transport units enhances not only device performance of PtAu3 cluster
complexes but also charge carrier abilities, which were analyzed through space charge limited current measurements.
Rational selection of complementary ligands to modulate the
shape and the energy of emission spectra results in either
Introduction
3
broad structureless emission (dominant MLCT character)6 or
Phosphorescent organic light-emitting diodes (PhOLEDs)
based on metal complexes have received growing attention
from academic research and commercial industry for full-color
flat panel display and energy-efficient lighting devices.1
Nevertheless, some major issues remain in current PhOLEDs to
be solved in the practical applications. Great progress has been
made to improve the device performance of PhOLEDs, but
most of them exhibit broad emission bands with a full width at
emission bands with vibronic features (dominant 3LC
character).7 The unsatisfactory emissive properties hinder the
further development of PhOLEDs by compromising the color
purities in displays. Recently, a promising molecular design
strategy has been proposed by systematic variation of ligands
using
cyclometalated Pt complexes8 so that the FWHM of emission
bands could be modulated in the range of 18 85 nm.
pyrazolyl-carbazole
groups
in
tetradentate
−
half maximum (FWHM) typically 80−100 nm. Although a
Polynuclear cluster complexes with judicious molecular
architectures exhibit distinct phosphorescence nature with
high PLQYs (nearly unity), superior solubility, film-forming
ability, morphological stability, and balanced charge carrier
ability so that they are ideal candidates for solution-processed
OLEDs.9-13 More importantly, phosphorescent polynuclear
cluster complexes display several advantages over
mononuclear complexes, such as (i) high molecular rigidity
originated from d8-d10/d10-d10 intermetallic contact leading to
intense phosphorescence, (ii) emission color tunability by
simply changing the bridging and ancillary ligands, (iii) plentiful
phosphorescent characteristics related to multiple metal ions
as well as intermetallic contacts, and (iv) LMCT/LLCT
dependent phosphorescence with narrow band emission
bands, typically FWHM of <70 nm, which are much smaller
than the utmost of monometallic complexes.14
plethora of cyclometalated Pt2 and Ir3 complexes for PhOLEDs
with high phosphorescent quantum yields (PLQYs) and short
emissive lifetimes have been reported, more investigations on
emissive dopants are still needed, because they generally
exhibit broad emission spectra.4 The phosphorescence in those
metal complexes originates mostly from the lowest triplet
excited states (T1) contributed by ligand-centered state (3LC)
and metal-to-ligand charge transfer character (3MLCT).5
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the
Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, China
*E-mail: czn@fjirsm.ac.cn;zhangxu@fjirsm.ac.cn
‡Dr.N. Nagarajan and L.-X. Shi contributed equally
Electronic Supplementary Information (ESI) available: Synthetic procedures of
ligands, computational studies and additional spectra. For ESI and crystallographic
data in CIF (CCDC 1882962-1882963) or other electronic format see
DOI:10.1039/x0xx00000x
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Journal Name
Recently, we observed that PtAu3 heterometallic cluster 31P [1H] NMR spectroscopy. The structures of complexes
View Article1Oanlninde
DOI: 10.1039/C8TC06384B
4 were determined by single crystal X-ray diffraction (Fig. 1).
complexes
supported
by
C3
symmetrical
tris(diphenylphosphinomethyl)phosphine (tdpmp) exhibited In the 1H NMR spectra, the three CH2 protons of tdpmp
distinct structural feature, in which the Pt atom in the PtAu3 appeared as two broad singlets in the range of 3.4−4.2 ppm (Fig.
cluster is bound to one of the terminal P donors in tdpmp so S1), which matches with the presence of two different
that the Pt is situated at one apex in the triangle plane of the environments in PtAu3 complexes. The 31P [1H] NMR spectra
PtAu3 cluster.15 Since the spatial alignment of aromatic of PtAu3 complexes (Fig. S2) exhibit three groups of signals
acetylides bound to PtAu3 backbone can be easily altered to centered at ca. 4.5−5.2 (JPt-P = 2696−2706 Hz), 17.8−22.7 and
result in improved or suppressed metal-ligand interaction 29.1−30.4 ppm. The first one is ascribed to one terminal P
depending on the spatial orientations, our further design donor of tdpmp bound to the Pt center, whereas the second one
strategy focuseson systematic modulation of structure and π- to the central P donor and the last triplet signal to the other two
conjugation of aromatic acetylides and their charge carrier terminal P donors bonded to Au(I) centers.
capability. In this article, five PtAu3 complexes 1−5 (Scheme 1)
with high PLQYs of 80.5%
The photoluminescence spectra of these complexes exhibit
structureless narrow to broad emission bands (FWHM = 38 72
−90.1% in doped films are reported.
−
nm) in CH2Cl2 solution and their structural alignments were
analyzed by crystallography and computational calculations.
The electroluminescence (EL) performance of solution-
processed OLEDs based on complex
green emission with FWHM of 42 nm, EQE of 10.3 %, CE of
38.7 cd A-1, PE of 22.9 lm W-1 andCIE (0.30, 0.61). Complex
1 exhibits narrow pure
4
having acetylide with phenathrene-functionalized 2-carbazole
substituent exhibited excellent device performance with CE of
62.2 cd A-1, PE of 30.3 lm W−1 and EQE of 16.6 %.
Fig 1.Perspective views of cationic PtAu3 complexes1 (a) and 4 (b) with 30% thermal
ellipsoids. Phenyl rings on the phosphorus atoms were omitted for clarity.
The crystal structure of complex
1
contains two
independent PtAu3 moieties. As revealed by X-ray
crystallography (Fig. 1), the structure of PtAu3 cluster
supported by two tdpmp in a
4-bridging mode shows a
triangle-planar arrangement, in which one Au atom is located
at the center whereas the Pt and other two Au atoms at the
three apexes. The PtAu3 cluster structure is further stabilized
by six five-membered coordination rings, additional Au-Cl-Au
linkage and substantial Pt
contacts. The Pt−Au (2.9633(4) Å for
and Au Au (2.9635(4) 2.9877(4)
2.9693(3) 3.0159(3) Å for ) distances are much shorter than
−
Au and Au
and 2.9348(3) Å for
for and
−Au intermetallic
1
4)
Scheme 1Synthetic routes to PtAu3 cluster complexes 1−5.
−
−
−
4
Å
1
the sum of the van der Waals radii for platinum and gold
atoms (3.38 Å) and that for two gold atoms (3.32 Å),
respectively, implying significant intermetallic contact and
noticeable aurophilicity.15 The Pt center is surrounded by
trans-arranged C2P2 donors to give square-planar geometry
Results and Discussion
Synthesis and Characterization
The synthetic routes to PtAu3 heterometallic cluster complexes
1−5 are illustrated in Scheme 1. Complexes 1−5 were prepared
with the C-Pt-C and P-Pt-P angles of 175.8(3) and 174.94(7)
for and 173.9(2) and 174.90(5) for , respectively. The Au
atoms are located in T-type environment composed of ClP2
donors with the P-Au-P angles of 172.65(7) 179.34(7) for
and 163.65(6) 177.30(5) Å for . The dihedral angles between
the planes of aromatic acetylides and PtC2P2 square plane are
13.9 to 45.4 in complex , which are much smaller than that

by the reactions of Pt(PPh3)2(CCR)(CCR’) (1 eq), tdpmp (2
eq), Au(tht)Cl (3 eq), and NH4ClO4 (3 eq) in CH2Cl2 solutions.
The products were then purified by chromatography on silica
gel columns using CH2Cl2/MeOH (v : v = 20 : 1) as the eluent
to give pure solids in good yields (66−74%). They were
1

4
−

1
−
4
1
satisfactorily characterized by HRMS (ESI) as well as H and

1
2 | J. Name., 2012, 00, 1-3
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in complex
4 (86.9). The better co-planarity in complex 1
View Article Online
DOI: 10.1039/C8TC06384B
1.0
0.8
0.6
0.4
0.2
0.0
(FWHM of49 nm, Table 1) is closely relevant to a much
narrower emission band than that in complex
nm).
1 (298 K)
1 (80 K)
4 (298 K)
4 (80K)
4 (FWHM of102
(a)
1.0
0.8
0.6
0.4
0.2
0.0
1
2
3
4
5
450
500
550
600
650
700
Wavelength (nm)
Fig. 3 Photoluminescence spectra of complexes
1 and 4 in doped films at 298 and

80 K, respectively.
250 300 350 400 450 500 550
Wavelength (nm)
Photoluminescence Properties
Complexes 1−5 (Fig. 2b) display Gaussian-like emission bands
peaked at 533 578 nm with moderate luminescence intensity
(b)
−
1.0
0.8
0.6
0.4
0.2
0.0
in degassed CH2Cl2 solutions, but the emission becomes much
stronger in solid states (Table 1). The luminescent lifetimes are
1
2
3
4
5
in the range of 2.1
−2.8
s in CH2Cl2 solutions at room
temperature and become 4.2
−
12.3 s in mCP : OXD-7

matrixes. The large Stokes shifts with microsecond range of
emissive lifetimes are characteristic of triplet excited states.
The close resemblance of PL spectra in doped films to those in
fluid CH2Cl2 solutions indicate that the emission originates
from the triplet excited states of unimolecular complexes. The
low-temperature emission spectra of complexes 1−5 are
similar to those measured at ambient temperature with
Gaussian-like shape but with noticeable sharpening of the
500
550
600
650
Wavelength (nm)
Fig.2 (a) The UV-Vis absorption spectra of complexes
1
−
5
in CH2Cl2 solutions at
in
room temperature. (b) The photoluminescent spectra of PtAu3 complexes 1−5
fluid CH2Cl2. The solution concentration is 1

10−5 M.
emission bands (FWHM = 29−58 nm) at 80 K (Fig. 3 and Fig.S3).
The photoluminescence origin is assigned to the admixture of
3LMCT and 3LLCT transitions, corresponding to aromatic
acetylide-to-PtAu3 and aromatic acetylide-to-tdpmp charge
transfer states, respectively.15 The PL spectra were
sequentially modulated from green to orange wavelength
range. The emission wavelengths can be correlated with the π-
conjugation and electron donating ability of aromatic
acetylides. The PL spectra of 1−5 in pure solid state are
UV-Vis Absorption Properties
The UV-Vis absorption and photoluminescence (PL) spectra of
complexes 1−5 in CH2Cl2 solutions are shown in Fig. 2. As
depicted in Fig. 2a, complexes
absorption bands in the range of 250−280 nm, originated from
tdpmp−centered π → π* transitions. A band centered at
290−380 nm is ascribed to the π → π* transition involving
aromatic−acetylides. More importantly, broad low-energy
bands centered at above 400 nm (ε= 1.2−2.7
cm−1) varies with respect to the extended π-conjugation and
1−5 exhibit an intense UV
obviously broader (FWHM = 49
−102 nm) with lower PLQY

104 dm3 mol−1
(7.4 41.5%) than those in doping films (Table 1), attributable
−
to the strong molecular aggregation as well as intermolecular
interaction.17 Concentration-dependent PL spectra (Fig. S4 and
electron donating ability of aromatic acetylide ligands.
Compound
on both sides of the Pt center shows absorption band peaked
at 416 nm. Compound with a C C-4-C6H4-(N-phenyl)benzImd
on one the side and electron-donating C C-3-PhCarb-9 on the
other side of Pt center displays a red-shifted absorption band
peaked at 440 nm. Compound with C C-3-PhCarb-9 on both
side shows band peaked at 474 nm. Compound with C C-2-
PhenCarb (N-Me)2 exhibits a low-energy band at 466 nm,
whereas it is red-shifted to 480 nm for with an extended π-
1 with two CC-4-C6H4-(N-phenyl)benzImd ligands
Table S1) in the doping films of
1 or 4 suggest that the
emission spectra show some blue-shift with the decrease in
the doping concentration of PtAu3 species, but the molecular
aggregation and concentration quenching are well suppressed
to exhibit a nearly constant emission band and FWHM when
the doping concentration is lower than 8wt%. The PL spectra
of 1−5 (Table 1) in doping films composed of 47.5 wt% mCP :
47.5 wt% OXD-7 : 5 wt% PtAu3 are peaked at 528, 543, 556,
558 and 572 nm respectively. The quite high PLQY (80.5−90.1
%) of the spin-coated films thus enables them as excellent
candidates for solution-processable OLEDs.
2


3

4

−
5
conjugation from 3-SpiroCz. The low-energy band arises most
likely from aromatic acetylide-to-platinum(II) ligand-to-metal
charge-transfer (LMCT) as well as aromatic acetylide-to-tdpmp
ligand-to-ligand charge-transfer (LLCT) transitions14a,14c,16 as
further confirmed by TD-DFT calculations (Tables S3−S6).
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DOI: 10.1039/C8TC06384B
Table 1.The Photoluminescence Data for PtAu3 Cluster Complexes 1−5 at Ambient Temperature.a

PL (nm)
 (s)
PLQY (%)
FWHM (nm)
CH2Cl2/powder/filmb)
CH2Cl2/powder/filmb)
CH2Cl2/powder/film b)
CH2Cl2/powder/filmb,c)
1
2
533/543/528
558/578/543
2.4/5.9/12.3
2.3/2.8/4.3
1.5/41.5/90.1
2.1/16.9./84.2
38/49/41 (29)
54/85/56 (45)
3
4
5
568/582/556
568/564,599/558
578/604/572
2.8/2.3/5.1
2.1/2.0/5.9
2.5/2.0/4.2
2.5/7.8/80.5
3.2/9.3/87.3
2.8/7.4/82.5
65/83/75 (57)
56/102/51 (36)
72/94/69 (58)
aAbsolute quantum yields in CH2Cl2 solutions, powder states and doping films were determined by the integrating sphere (142 mm in diameter). bComposed of 47.5
wt% mCP : 47.5 wt% OXD-7 : 5 wt% PtAu3 complex. c The data in parentheses were measured at 80 K.
Table 2. The Contributions (%) of Each Fragment in Complexes 1−5 to “Electron” and “Hole” in the Lowest-energy Triplet State in CH2Cl2 Solution by SCPA Method with TD-DFT at
the PBE1PBE Level.a
complex
MO contribution (%)
Pt (s/p/d)
Au (s/p/d)
tdpmp
39.95
4.13
42.23
3.56
56.88
3.5
43.67
5.37
R-CC
15.62
80.17
6.63
80.5
2.4
85.08
12.84
81.48
1.88
Cl
0.62
0.3
1
2
3
4
5
electron
hole
electron
hole
electron
hole
electron
hole
15.99 (61/22/17)
11.64 (1/7/92)
22.43(67/16/16)
11.87(1/9/91)
2.32(1/88/10)
9.64(2/1/97)
15.78(68/18/13)
4.72(4/11/85)
8.83(79/17/5)
10.1(4/5/91)
27.80 (55/40/5)
3.75 (38/28/34)
27.91(43/53/4)
3.82(45/27/28)
38.27(45/44/11)
1.54(26/38/36)
27.30(44/48/8)
8.09(49/27/24)
38.22(41/50/9)
4.36(55/18/27)
0.79
0.24
0.12
0.24
0.41
0.33
0.12
0.39
electron
hole
50.93
4.35
80.8
a The “electron” and “hole” represent electron accumulation (EA) and electron depletion (ED) in the transition process, respectively.
Table 3.Transferred Electrons in the LLCT and LMCT Processes in the Lowest-energy Triplet States for Complexes 1−5 in CH2Cl2 Solutions by SCPA Method with TD-DFT at the
PBE1PBE Level.
LMCT
complex
LLCT (RCC →tdpmp)
RC
C
→
Pt
RC
C
→
Au
RCC → PtAu3 (sum)
1
2
3
4
5
0.31752
0.33816
0.48319
0.35190
0.41077
0.11084
0.17362
0.01739
0.12145
0.06953
0.21241
0.22068
0.3252
0.21006
0.30798
0.32325
0.3943
0.34259
0.33151
0.37751
The FWHM (Table 1) for the PL spectra of
nm) and
than those of
followed in 5 wt% doping films (Table 1) with the FWHM of 41,
56, 75, 51 and 69 nm for complexes 1−5, respectively. Taking
advantage of the optimized geometry in the lowest triplet
state, the dihedral angles between the plane of aromatic
acetylide and PtC2P2coordination square plane can be
calculated accordingly. The distinctly smaller dihedral angles in
1
(38 nm), 2 (54 Theoretical Computational Studies
4
(56 nm) in fluid solutions were obviously smaller
(65 nm) and (72 nm). This trend was also
To factually address the fluctuations in narrow emission
behavior with respect to the π-conjugation and electron
donating ability of aromatic acetylide, TD-DFT calculations
were performed on both the ground and lowest-energy triplet
3
5
states for complexes 1−5 (Tables S3-S18). It can be seen that
the HOMO (Fig.s S5 and S6) focuses predominately on
aromatic acetylides (>79 % population) for all these complexes
with much less distribution on Pt and Au centers (<18 %
population). In contrast, the LUMO is populated over tdpmp,
Pt and Au centers and the distribution percentage changes
with respect to the π-conjugation extent and electron
donating ability of aromatic-acetylide. Accordingly, the
1
(13.6 and 29.5

),
2
(22.2 and 33.7
) and

5
) and
(38.1 and 69.0
4
(11.3 and 44.4
)
than those in (69.6 and 69.6
clearly that the formers display better orbital overlap18
between Pt coordination plane and aromatic acetylide,
3

) reveal
whereas the lower co-planarity is observed in
3 and 5.
electron transition of HOMO
energy singlet (S1) and triplet (T1) states is mainly featured
with (aromatic acetylide) →* (tdpmp) LLCT and (aromatic
acetylide) s/p (Pt/Au) LMCT states.
→LUMO in both the lowest-
Obviously, the better co-planarity between Pt coordination
square plane and aromatic acetylide is in favor of giving
narrower emission bands.


→
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and “hole” in the lowest-energy triplet states of complexes
View Article Online
1−5
in CH2Cl2 is summarized in TablDeO2I:.10T.1h0e39/tCr8aTnCs0fe63rr8e4dB
electron between individual fragments in the LLCT and LMCT
processes are also presented in Table 3.
As depicted in Fig. 4, the hole (electron loss) in PtAu3 cluster
complexes
Table 2), whereas the transferred electron is spread over PtAu3
cluster (40.59% 50.34%) and tdpmp (39.95% 56.88%).
Noticeably, the transferred electron is less populated on
1−5 focuses mostly on aromatic acetylides (> 80%,
−
−
tdpmp in
(56.88%) and
1
(39.95%),
2
(42.23%) and
4
(43.67%) than that in
(0.33816) and
3
4
5
(50.93%), so that
1
(0.31752), 2
(0.35190) (Table 3) exhibit obviously less LLCT character than
that in (0.48319) and (0.41077). On the other hand, the
transferred electron is more populated on Pt and less on Au
for (15.99% on Pt and 27.80% on Au), (22.43% on Pt and
27.91% on Au), and (15.78% on Pt and 27.30% on Au) than
that for (2.32% on Pt and 38.27% on Au) and (8.83% on Pt
and 38.22% on Au). On this basis, complexes (0.11084),
(0.17362) and (0.12145) display more aromatic acetylide-
to-Pt LMCT character than that in (0.01739) and (0.06953)
as indicated in Table 3. As a result, the distinctly narrower
FWHM of the emission bands for complexes (38 nm), (54
nm) and (56 nm) than those for (65 nm) and (72 nm) in
CH2Cl2 solutions are well correlated to the more aromatic
3
5
1
2
4
3
5
1
2
4
3
5
1
2
4
3
5
acetylide-to-Pt LMCT character (0.11084 for
1
, 0.17362 for
2
and 0.12145 for versus 0.01739 for and 0.06953 for
4
3
5
) but
less aromatic acetylide-to-tdpmp LLCT percentage in the
formers.18
Fig. 4 Plots of the “hole” (green part) and “electron” (purple part) (isovalue = 0.0004) in
the lowest-energy triplet states for PtAu3 cluster complexes 1−5 in CH2Cl2 solutions by
TD-DFT method at the PBE1PBE level. The process of single-electron excitation can be
described as an electron leaving from “hole” and going to “electron” part.
Solution-Processed OLEDs
The EL performance (Table 4) of complexes
phosphorescent dopants was achieved in solution-processed
OLEDs. As depicted in Fig.5, employing 5 wt% 1 5 : mCP : OXD-
1−5 as
−
7 (wt%, 1 : 1) doping films as emitting layers (EML), three-layer
devices were fabricated with the structure ITO/PEDOT : Poly-
TPD (50 nm) / EML (50 nm) / ETL (50 nm) / LiF (1 nm) / Al (100
To get more insight into the influence of the substitution on
the excited-state transition process and the FWHM of the
emission band, analysis of hole-electron distribution was
introduced to overcome the defect by analyzing the transition
of multiple MO pairs with corresponding weighting coefficients.
The process of single-electron excitation can be described as
an electron leaving “hole” and going to “electron”. According
to the definition of “hole” and “electron” by Lu et al,19 the
analysis of hole and electron distribution and inter-fragment
charge transfer (IFCT) by using Multiwfn program is an
effective approach to examine the electronic excitation
process. The contribution of each fragment to the “electron”
nm). The poly(3,4-ethylenedioxythiophene)
:
poly(4-
butylphenyldiphenylamine) (PEDOT: Poly-TPD) was used as
hole-injection layer through spin-coating in an aqueous
solution. The emissive layer was prepared by spin-coating a
solution of mCP : OXD-7 (1:1) : PtAu3 complex (5 wt%) blend in
dichloromethane. To improve the charge balance and achieve
better exciton recombination zone, an additional layer with
BmPyPb was introduced to serve as electron transport/hole
blocking layer, which was then capped with LiF/Al cathode.
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Journal of Materials Chemistry C
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ARTICLE
Journal Name
Table 4.The Performance Data of Solution-processed OLEDs Based on Phosphorescent PtAu3Cluster Complexes1−5.a
View Article Online
DOI: 10.1039/C8TC06384B
complex
EL /nm
1
527
2
539
3
565
4
556
5
568

FWHM/nm
Vonb)/V
42
3.0
62
3.4
92
3.5
59
4.2
83
5.4
Lmaxc)/cd m−
10415
38.7
22.9
10.3
0.30, 0.61
17079
55.6
35.1
14.8
0.33, 0.60
14755
45.5
28.3
14.1
0.47, 0.52
6539
62.2
30.3
16.6
0.54, 0.32
12702
57.1
20.1
13.1
0.46, 0.54
2
CEmaxd)/cd A−
1
PEmaxe)/lm W−
EQEmaxf)/%
CIE
1
a)Device structure is ITO / PEDOT : Poly-TPD (50 nm) / mCP (24 wt%) : OXD-7 (47 wt%) : PtAu3 complex (5 wt%) (50 nm) / BmPyPb (50 nm) / LiF (1 nm) / Al (100 nm).
b)Turn-on voltage at 1 cd m−
.
c)Maximum luminance. d)Maximum current efficiency. e)Maximum power efficiency. f)Maximum external quantum efficiency.
2
Fig.5 (a) Energy level diagram of the transport materials and emitting compounds
and (d) EL spectra of the devices based on PtAu3 complexes
1−5 used in the devices, (b) current efficiency vs luminance, (c) EQE vs luminance,
1−5.
The EL performance parameters of PtAu3 complexes1−
5 are 38.7 cd A-1, PE of 22.9 lm W-1, and the CIE (0.30, 0.61). Such a
listed in Table 4.The current efficiency (CE) vs luminance, narrow-band emission with EQE over 10% represents superior
external quantum efficiency (EQE) vs luminance and the EL device performance for solution-processed OLEDs. The device
spectra of the devices are depicted in Fig.5. The turn-on based on complex
2 also exhibit green emission peaked at 539
voltages of these devices are relatively low, ranging from 3.0– nm and CIE (0.33, 0.60) with the peak CE of 55.6 cd A-1 PE of
,
5.4 V (Table 4) and the OLEDs exhibit intense green to 35.1 lm W-1 and EQE of 14.8%, but a broader emission band
yellowish orange electroluminescence with the emission bands with the FWHM of 62 nm. The distinctly improved efficiency
peaked at 527–568 nm. The EL spectra of the optimized for
devices are virtually identical to the corresponding PL spectra character in the presence of both hole-transport (C
of the doping films. No residual emission from the host (N-phenyl)benzImd) and electron-transport (C C-3-PhCarb-9)
2
compared with that for
1
arises likely from the bipolar

C-4-C6H4-

materials was observed when the doping concentration of 5% ligands, in which the devices achieve a better balance of
PtAu3 complexes was used. The excitons were completely electron and hole carriers at the interface of the emissive
confined within the emissive layer and charge carrier layer.20 The PtAu3 cluster complexes having acetylides with 2-
recombination took place only in the emissive layers of the or 3-carbazole (
devices. Of the devices based on PtAu3 complexes with the spiro-carbazole (
same architecture, the devices based on complex exhibited variations in contour of the EL spectra and device performance.
pure green electroluminescence and the narrowest emission Complexes and contain acetylides with 3-carbazole
band with the FWHM of 42 nm, the peak EQE of 10.3%, CE of substituent exhibited FWHM of 92 and 83 nm, CE of 45.5 and
3
), structurally fused phenathrene (
4) and
5
) connected to the Pt showed dramatic
1
3
5
6 | J. Name., 2012, 00, 1-3
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Hole mobility
휇 = 휇0exp
(훾 퐸)
√
(2)
Page 7 of 12
Journal of Materials Chemistry C
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Journal Name
ARTICLE
57.1 cd A-1 as well as EQE of 14.1 and 13.1 %, respectively, where γ is the field dependence parameter and μo is the zero-
View Article Online
while acetylides with 2-carbazole unit in complex
4
exhibited field mobility. In this case, the expressioDnOfIo: 1r0t.1h0e39S/CCL8CTCc0a6n38b4eB
FWHM of 59 nm, CE of 62.2 cd A-1 and EQE of 16.6 %. The approximated by using the empirical Murgatroyd equation:
slight broadening observed in the EL spectra relative to those
in the doping films is possibly due to

-

interaction of PtAu3
퐽 = 9휀 휀 푉2휇 exp(0.891훾 푉/퐿) /8퐿3
(3)
√
0
푟
0
species with host molecules.21 It is noteworthy that the
emission bands in PtAu3 complexes having the acetylides with where V is voltage. The values of μo and γ were obtained by
2-carbazole units are obviously narrower than those having fitting the experimental J-V curves of electron- and hole-only
the acetylides with 3-carbazole units.
devices in SCLC region according to equation (3).
The impressive device performances should be closely
related to the design concept that the use of ethynyl ligands
with the 2-carbazole groups supports the structural co-
planarity with Pt coordination square plane so as to give
narrower emission bands, which can also provide enhanced
charge carrier transport ability in PtAu3 complexes to improve
EL efficiency. Upon carefully examining the emission bands in
(a)
104
103
102
101
hole
only
electron
only
100
the recently reported PtM2 (M
=
Au or Ag)
1
1
2
3
4
complexessupportedby dpmp (bis(diphenylphosphinomethyl)-
phenylphosphine),14a,14e we can find the similar phenomenon,
in which the emission bands in PtM2 complexes having
acetylides with 2-carbazole ligands are much narrower than
those having acetylides with 3-carbazole or 4-carbazole ligands.
Consequently, it is evident that merely enhancing the co-
planarity of aromatic acetylide with Pt coordination square
plane could improve the orbital contribution of Pt in charge
transfer processes so that more acetylide-to-Pt LMCT
character is achieved to give narrower emission bands.
10-1
2
3
4
10-2
0.1
1
10
Voltage (V)
(b)
4.0x10-7
3.0x10-7
2.0x10-7
Electron mobility
1.0x10-7

0.0
Charge Transport Properties
2.0x10-7
1.5x10-7
1.0x10-7
5.0x10-8
In order to understand the influence of structural variation on
device performance, the charge carrier mobility of complexes
1
−
4 was investigated by the space-charge limited current
(SCLC) technique.22-24 Fig.6a shows current density-voltage (J-V)
characteristics of complexes in electron-only devices with

1−4
1
2
Compound Number
3
4
the configuration of ITO/LiF (2 nm)/EML (60 nm)/LiF (2 nm)/Al
(100 nm) and hole-only devices with the configuration of
ITO/PEDOT:PSS (70 nm)/EML (60 nm)/MoO3 (2 nm)/Al (100 nm)
under ambient conditions. It can be seen that the J-V behavior
is ohmic and the dependence of current density on voltage is
linear at low voltages. While raising the applied voltage,
injection of charge carrier took place and the current became
space charge limited, which is quadratic dependence on the
voltage. In this regime, the SCLC characteristics are generally
described by the following Mott-Gurney equation:
Fig.6 (a) J-V characteristics of electron-only and hole-only devices of complexes 1−4. (b)
Electron and hole mobility of complexes 1−4 in the electric field of 1.5  106 V cm−
1
calculated by SCLC technique.
The charge mobility at a given field then can be calculated
according to Equation (2). As shown in Fig. 6b, the electron
mobility shows a stepwise decrease in the order 3.94
3.24 2) > 1.76 ) > 0.18
10-7 10-7 10-7 cm2 V-1 cm-1
electric field of 1.5
exhibits a reversed order following 0.37
2)< 1.71 ) < 2.11
10-7 10-7 cm2 V-1 s-1

(
10-7
4) at an
(
1
) >

(


(
3

106 V cm-1. In contrast, the hole mobility
퐽 = 9휀0휀푟휇E/8L
Where J is current density, εo is the free space permittivity
(8.85
10-14 C V-1 cm-1), εr is the relative dielectric constant
(1)

10-7
(1) < 0.79
10-7
(

(3

(4). The comparable

hole and electron mobility in these PtAu3 complexes provides
an excellent carrier balance in the emitting layers so that
superior electroluminescence performance with the CE over
(calculated to be 99 by using Tonghui TH2828 precision LCR
meter), E is the electric field, and L is the thickness of the
active layer. In general, the carrier mobility (μ) depends on the
electric field (E) and is thus described by the Poole-Frenkel
formalism:
38 cd A− and the EQE over 10% can be achieved in solution-
1
processed devices. On the other hand, it is known that
benzo[d]imidazole and carbazole are favorable electron- and
hole-transport groups, respectively. Since complexes
contain two benzo[d]imidazole, one benzo[d]imidazole and
one carbazole, and two carbazole groups, respectively, it is
easy to understand the order of electron mobility and
1, 2, and
3
1 > 2 > 3
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Journal of Materials Chemistry C
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ARTICLE
Journal Name
that of hole mobility 1 < 2 < 3. In view of a larger -conjugation CH2Cl2-petroleum ether as eluent. The procedure for the
View Article Online
system in dibenzo[a,c]carbazole than that in carbazole, the synthesis
of
tris((diphenylphosphDinOoI:)m10.e1t0h3y9/l)Cp8hToCs0p6h38in4Be
former is a better hole-transport moiety than that of the latter. (tdpmp) followed the method reported in the literature.28
Thus, it is reasonable that complex
dibenzo[a,c]carbazole moieties provides a higher hole mobility (ClO4)2 (1).
4
with two
[PtAu3(

-Cl)(tdpmp)2(C

C-4-C6H4-(N-phenyl)benzImd)2]
C-4-C6H4-(N-
A
mixture of Pt(PPh3)2(C

than that of complex
3
with two carbazole groups.
phenyl)benzImd)2 (65.2 mg, 0.05 mmol), tdpmp (62.7 mg, 0.1
mmol), Au(tht)Cl (48 mg, 0.15 mmol) and NH4ClO4 (18 mg, 0.15
mmol) was added to CH2Cl2 (30 mL) with stirring at ambient
temperature for 8 h. The product was then purified by
chromatography on a silica gel column using CH2Cl2/MeOH (20 :
1) as eluent. Yield: 70%. HRMS (ESI): m/z calculated for
Conclusions
The structural uniqueness of tetraphosphine-supported PtAu3
cluster complexes encourages us to design and synthesize
C120H98Au3ClN4P8Pt [M
−
2ClO4]2+: 1332.1989; found: 1332.2010.
7.91 (m, 8H), 7.80 7.82 (m, 10H),
7.49 (m, 18H), 7.34 7.36 (m, 6H),
7.29 (m, 18H), 6.99 (t, 6H, J = 7.2 Hz), 6.94 (d, 4H, J = 8.4
various
aromatic
acetylide
ligands
to
modulate
1H NMR (CDCl3, ppm): 7.89
−
−
−
phosphorescent emission properties. The structural difference
of aromatic acetylides modifies the spatial alignment of the
PtAu3 cluster complexes so that the band width of emission
spectra could be modulated. Both structural and theoretical
studies indicate that the co-planarity of aromatic acetylide
with Pt coordination square plane is in favor for acetylide-to-Pt
3LMCT state to achieve narrow-band emission. The PtAu3
cluster complexes not only exhibit excellent solubility in
organic solvents with robust chemical and thermal stability,
but also show bright phosphorescence with PLQY up to
7.57
7.26
−
−
7.61 (m, 12H), 7.45
−
Hz), 5.30 (d, 4H, J = 8.4 Hz), 4.07 (br, 4H), 3.54 (br, 4H), 3.46 (br,
4H). 31P NMR (CDCl3, ppm): 30.4 (t, 4P, JP = 31 Hz), 22.6 (m,
−
P
2P, JP P = 30 Hz), 3.9 (t, 2P, JP P = 29 Hz, JPt P = 2686 Hz). IR (KBr,
−
−
−
−
1
−
cm ): 2092w (C≡C), 1100s (ClO4 ).
[PtAu3( -Cl)(tdpmp)2(C C-4-C6H4-(N-phenyl)benzImd)(C
3-Ph-9-Carb)](ClO4)2 (2). This compound was prepared by the
same synthetic procedure as that of except for the use of


C-
1
Pt(PPh3)2(C≡C-4-C6H4-(N-phenyl)benzImd)(C≡C-3-Ph-9-Carb)
instead of Pt(PPh3)2(C≡C-4-C6H4-(N-phenyl)benzImd)2. Yield:
74 %. HRMS (ESI): m/z calculated for C119H97Au3ClN3P8Pt
80.5%−90.1% in doping films. Highly efficient solution-
processed OLEDs were fabricated when 5wt% PtAu3 complexes
were doped with blended host materials of mCP and OXD-7 as
the emitting layers. The devices with peak CE of 38.7 cd A−1
and EQE of 10.3% and FWHM of 42 nm, and CE of 62.2 cd A−1,
EQE of 16.6% and FWHM of 59 nm were realized for
[M
ppm): 8.02
8H), 7.58 7.62 (m, 4H), 7.49
22H), 7.24 7.26 (m, 6H), 7.04
−
2ClO4]2+: 1318.6934; found: 1318.6961. 1H NMR (CDCl3,
8.06 (m, 4H), 7.74 7.81 (m, 16H), 7.65 7.69 (m,
7.52 (m, 12H), 7.37 7.46 (m,
7.06 (m, 4H), 6.93 6.95 (m, 4H),
−
−
−
−
−
−
−
−
−
complexes
1 and 4,respectively, which are the ones among
6.72 (d, 1H, J = 8.4 Hz), 6.01 (s, 1H), 5.70 (d, 1H, J = 8.0 Hz),
5.42 (d, 2H, J = 8.0 Hz), 4.04 (br, 4H), 3.86 (br, 4H), 3.69 (br,
4H). 31P NMR (CDCl3, ppm): 29.4 (t, 4P, JP = 31 Hz), 17.9 (m,
excellent narrow-band emissive devices based on the solution-
processed OLEDs.
−
P
2P, JP P = 31 Hz), 5.5 (t, 2P, JP P = 30 Hz, JPt P = 2686 Hz). IR (KBr,
−
−
−
−
−
1
cm ): 2104w (C≡ C), 1100s (ClO4 ).
[PtAu3( -Cl)(tdpmp)2(C C-3-Ph-9-Carb)2](ClO4)2 (3). This
compound was prepared by the same synthetic procedure as
that of except for the use of trans-Pt(PPh3)2(C C-3-Ph-9-
Experimental Section
General Procedures and Materials


Aromatic acetylide ligands including (2-(4-ethynylphenyl)-1-
1

phenyl-1H-benzo[d]imidazole)
phenyl)benzImd), 3-ethynyl-9-phenyl-9H-carbazole (HC
Ph-9-Carb), 11-ethynyl-9-methyl-9H-dibenzo[a,c]carbazole
(HC C-2-PhenCarb(NMe)) and 2'-ethynyl-5'-methyl-5'H-
spiro[fluorene-9,11'-indeno[1,2-b]carbazole] (HC C-3-
(HC
C-4-C6H4(N-
Carb)2 instead of Pt(PPh3)2(C≡C-4-C6H4-(N-phenyl)benzImd)2.

C-3-
Yield: 66%. HRMS (ESI): m/z calculated for C118H96Au3ClN2P8Pt
[M
ppm): 8.01
10H), 7.51
−
2ClO4]2+: 1305.1880; found: 1305.1909. 1H NMR (CDCl3,

−
8.03 (m, 8H), 7.74
−
7.77 (m, 10H), 7.66 7.69 (m,
−

−
7.55 (m, 12H), 7.43
−
7.49 (m, 12H), 7.37−7.41 (m,
SpiroCarb(NMe)) were synthesized according to the modified
procedures25-27 and the experimental details are shown in
Supporting Information (Scheme S1). All the reactions were
conducted under dry argon using Schlenk technique and
vacuum-line system. All solvents were carefully dried and
distilled from appropriate drying agents prior to use. The
16H), 6.95 (m, 10H), 6.78 (d, 2H, J = 8.4 Hz), 6.02 (s, 2H), 5.78
(d, 2H, J = 8.4 Hz), 4.13 (br, 4H), 4.03 (br, 4H), 3.65 (br, 4H). 31P
NMR (CDCl3, ppm): 29.6 (t, 4P, JP = 32 Hz), 18.1 (m, 2P, JP
=
−
P
−
P
−
1
30 Hz), 6.2 (t, 2P, JP = 30 Hz, JPt = 2726 Hz). IR (KBr, cm ):
−
P
−
P
−
2099w (C≡C), 1100s (ClO4 ).
[PtAu3( -Cl)(tdpmp)2(C C-2-PhenCar(NMe))2](ClO4)2
This compound was prepared by the same synthetic procedure
as that of except for the use of trans- Pt(PPh3)2(C C-2-


(4).
precursor
phenyl)benzImd)2, Pt(PPh3)2(C
(C C-3-Ph-9-Carb),
Pt(PPh3)2(C C-2-PhenCarb(NMe))2
complexes
Pt(PPh3)2(C
C-4-C6H4-(N-phenyl)benzImd)-
C-4-C6H4-(N-

1


Pt(PPh3)2(C

C-3-Ph-9-Carb)2,
PhenCarb (NMe))2 instead of Pt(PPh3)2(C≡C-4-C6H4-(N-
phenyl)benzImd)2. Yield: 72%. HRMS (ESI): m/z calculated for

and
Pt(PPh3)2(C C-3-

SpiroCarb(NMe))2 were prepared by the reactions of
Pt(PPh3)2Cl2 (0.5 mmol), corresponding acetylide ligands (1.1
mmol), CuI (1 mg) and NEt3 (1 mL) in chloroform (50 mL) with
stirring for 5 h at 50 oC. The products were purified by
C124H100Au3ClN2P8Pt
[M
−
2ClO4]2+:
1343.2036;
found:
1343.2141. 1H NMR (CDCl3, ppm): 8.93 (d, 2H, J = 9.2 Hz), 8.84
(d, 2H, J = 8.0 Hz), 8.79 (d, 2H, J = 8.4 Hz), 8.73 (d, 2H, J = 9.2
Hz), 8.64 (d, 2H, J = 7.6 Hz), 8.02
−
−
8.08 (m, 8H), 7.84 (t, 4H, J =
7.68 (m, 6H), 7.44 7.48 (m,
chromatography on silica gel (100−200 mesh) columns using
7.6 Hz), 7.72 7.78 (m, 16H), 7.62
−
−
8 | J. Name., 2012, 00, 1-3
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Page 9 of 12
Journal of Materials Chemistry C
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Journal Name
22H), 7.00
ARTICLE
−
7.08 (m, 12H), 5.99 (d, 2H, J = 8.0 Hz), 5.49 (s, 2H), diffractometer using IμS 3.0 microfocus source Mo-Kα
View Article Online
4.07 (br, 4H), 3.98 (s, 6H), 3.73 (br, 4H), 3.55 (br, 4H). 31P NMR radiation (
DOI: 10.1039/C8TC06384B
 = 0.71073 Å) and PHOTON II CPAD detector.
(CDCl3, ppm): 29.8 (t, 4P, JP P = 32 Hz), 18.2 (m, 2P, JP P = 31 Hz), Frames were integrated with the Bruker SAINT software
−
−
−
1
6.5 (t, 2P, JP = 30 Hz, JPt = 2744 Hz). IR (KBr, cm ): 2099w package (V8.38A) using
a
SAINT algorithm. Data were
corrected for absorption effects using the multi-scan method
C-3-SpiroCarb(NMe))2](ClO4)2 (5). (SADABS).29 All the structures were solved and refined using
This compound was prepared by the same synthetic procedure the Bruker SHELXTL Software Package, a computer program
as that of except for the use of trans-Pt(PPh3)2(C C-3- for automatic solution of crystal structures, and refined by the
SpiroCarb(NMe))2 instead of Pt(PPh3)2(C≡C-4-C6H4(N- full-matrix least-squares method with ShelXle Version 4.8.6, a
phenyl)benzImd)2. Yield: 66%. HRMS (ESI): m/z calculated for Qt graphical user interface for the SHELXL.30
C146H112Au3ClN2P8Pt [M 1481.7506; found: Computational Details. To understand the electronic and
2ClO4]2+:
1481.7545. 1H NMR (CDCl3, ppm): 8.22 (d, 4H, J = 8.8 Hz), 8.02 spectroscopic properties, the calculations were implemented
(d, 2H, J = 7.6 Hz), 7.76 7.79 (m, 8H), 7.68
7.71 (m, 6H), by using Gaussian 09 program package31 for complexes
7.50 7.56 (m, 18H), 7.44 7.48 (m, 10H), 7.21 7.27 (m, 6H), The geometrical structures as isolated molecules in the ground
7.13 (t, 6H, J = 7.6 Hz), 7.01 7.04 (m, 12H), 6.84 (d, 4H, J = 7.6 state and the lowest-energy triplet state were firstly optimized,
Hz), 6.72 6.76 (m, 10H), 6.58 (t, 4H, J = 7.2 Hz), 5.56 (d, 2H, J = respectively, by the restricted and unrestricted density
−
P
−
P
−
(C≡C), 1100s (ClO4 ).
[PtAu3( -Cl)(tdpmp)2(C


1

−
−
−
1−5.
−
−
−
−
−
8.4 Hz), 5.41 (s, 2H), 4.04 (br, 8H), 3.90 (s, 6H), 3.56 (br, 4H). functional theory (DFT) method with the gradient corrected
31P NMR (CDCl3, ppm): 30.4 (t, 4P, JP = 33 Hz), 19.2 (m, 2P, correlation functional PBE1PBE.32 During the optimization
−
P
JP = 31 Hz), 5.7 (t, 2P, JP = 30 Hz, JPt = 2744 Hz). IR (KBr, process, the convergent values of maximum force, root-mean-
−
P
−
P
−
P
−
−
1
cm ): 2099w (C≡C), 1100s (ClO4 ).
square (RMS) force, maximum displacement and RMS
Physical Measurements. The H and 31P NMR spectra were displacement were set by default. To analyse the spectroscopic
performed on a Bruker Avance III (400 MHz) spectrometer properties, 80 singlet and 6 triplet excited-states were
with SiMe4 as the internal reference and H3PO4 as the external calculated, respectively, based on the optimized structures in
reference, respectively. Splitting patterns are designated as the ground state and lowest-energy triplet state to determine
singlet (s), doublet (d), and triplet (t). Splitting patterns that the vertical excitation energies by time-dependent density
could not be interpreted or easily visualized are designated as functional theory (TD-DFT)33 with the same functional used in
multiplet (m) and broad (br). The UV-Vis absorption spectra the optimization process. In the calculation of excited states,
1
were measured on
a
Perkin-Elmer Lambda 35 UV-Vis the polarizable continuum model method (PCM)34 with CH2Cl2
spectrophotometer using a 10 mm path quartz cell. The as solvent was employed. The self-consistent field (SCF)
infrared spectra (IR) were recorded on a Magna 750 FT-IR convergence criterions of RMS density matrix and maximum
spectrophotometer. The high-resolution mass spectrometry density matrix were set by default in the excited-state
(HRMS) was conducted on an Impact II mass spectrometer calculation. The iterations of excited states continue until the
using dichloromethane and methanol mixtures as mobile changes on energies of states were no more than 10-7a.u.
phases. The emission and excitation spectra together with the between the iterations, and then convergences reached in all
emissive lifetimes were measured on Edinburgh FLS-920 the excited states. In these calculations, the Stuttgart-Dresden
fluorescence spectrometer. The emission spectra were (SDD)35 basis set and the effective core potentials (ECPs) were
recorded by exciting the samples at their excitation spectral used to describe the Pt and Au atoms, while other non-metal
maxima unless otherwise mentioned. All the experiments in atoms of Cl, P, N, C and H were described by the all-electron
10− M. basis set of 6-31G**. Visualization of the frontier molecular
5
solutions were performed at a concentration of 1.0
The luminescent quantum yield (Φem

)
in degassed orbitals and the hole-electron distribution were performed by
dichloromethane solutions, powder samples and films at room GaussView. The contributions of fragments to “hole” and
temperature were determined by the integrating sphere (142 “electron” and InterFragment Charge Transfer (IFCT)19 in the
mm in diameter) using Edinburgh FLS-920 fluorescence electronic excitation process were analysed by the Ros&Schuit
spectrometer. The cyclic voltammetry was measured on CHI method36 (C-squared population analysis method, SCPA) in
660E electrochemical workstation (Shanghai CH Instruments) Multiwfn 3.3.8 program.37
in CH2Cl2 solution using 0.1
M
tetrabutylammonium
Device Fabrication and characterization. ITO substrates
hexafluorophosphate (TBAPF6) as the supporting electrolyte. were cleaned by detergent and deionized water, then
The experiments were performed at room temperature at 1 successively washed by ethanol, acetone, and isopropanol
mM concentration with a three-electrode cell that consists of a under ultrasonic, respectively, followed by UV-ozone
Pt wire as an auxiliary electrode, a saturated Ag/Ag+ reference treatment for 15 min. A PEDOT : PSS solution was spin-coated
electrode and a Pt working electrode. Ferrocene/ferrocenium on the ITO substrates at 4800 r/min for 1 min, which were
(Fc/Fc+) was used as an internal standard. The then dried at 140 oC for 20 min. The emitting layers were
thermogravimetric analysis (TGA) was performed under a prepared using filtered CH2Cl2 solutions (5 mg/mL) composed
continuous nitrogen flow using a TA Instruments Q50 at a of host and PtAu3 compound through spin-coating at 2000
heating rate of 10 °C min −1
Crystal Structural Determination
diffraction data were collected on a Bruker D8 Venture chamber at a base pressure lower than 4.0
.
r/min for 30 s. Subsequently, ETL (0.3 nm/s), LiF (0.05 nm/s)
.
X-ray single-crystal and Al (3 nm/s) were thermally evaporated in a vacuum
4

10− Pa. The
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Journal Name
Chem.,2005, 44, 1713; (b) Z. Wang, E. Turner, V. Mahoney, S.
current density-voltage-brightness (I-V-B) characteristics of the
devices were measured on a Keithley 2400/2000 source meter
with a calibrated silicon photodiode. All the measurements of
the devices were performed at dry and ambient conditions
with humidity lower than 30%.
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We are grateful for financial support from the National Natural
Science Foundation of China(Grants 21650110449, U1405252,
21531008, 21601184 and21473201), the CAS/SAFEA
International PartnershipProgram for Creative Research
Teams, and the StrategicPriority Research Program of the
Chinese Academy of Sciences(Grant XDB20000000).
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The table of contents entry
PtAu3 Cluster Complexes with Narrow-band Emission for Solution-Processed
Organic Light Emitting Diodes
Nagarajan Natarajan,∥ Lin-Xi Shi,∥ Hui Xiao, Jin-Yun Wang,* Li-Yi Zhang, Xu
Zhang, and Zhong-Ning Chen*
Solution-processed OLEDs based on PtAu3 cluster complexes show high-efficiency
electroluminescence with narrow emission bands through enhancing the co-planarity
between aromatic acetylide and platinum(II) coordination square plane.