Efficient deep-red electroluminescent donor-acceptor copolymers based on 6,7-dichloroquinoxaline

Article abstract of DOI:10.1016/j.orgel.2017.04.002

Since the large steric hindrance caused by chlorine atoms not only suppresses the aggregation but also results in large stokes shift and low self-absorption, a series of donor-acceptor alternating copolymers based on 6,7-dichloroquinoxaline have been synthesized by modifying the structures of oligothiophenes. All the polymers have been well characterized to study the effects of the length of oligothiophenes and the steric hindrance on the optical, electronic and electroluminescent properties. It was observed that the intramolecular charge transfer absorption was weakened by steric hindrance. Unlike non-chloride analogues, prolonged conjugated length resulted in smaller bandgap, given similar steric hindrance. Deep-red emission centered at 678?nm with brightness about 1800?cd?m^?2 was achieved with external quantum efficiency 1.34% using dopant/host technic.

Full text of DOI:10.1016/j.orgel.2017.04.002

Accepted Manuscript
Efficient deep-red electroluminescent donor-acceptor copolymers based on 6,7-
dichloroquinoxaline
Xiang Gao, Yubao Zhang, Cheng Fang, Xiang Cai, Bin Hu, Guoli Tu
PII:
S1566-1199(17)30150-7
10.1016/j.orgel.2017.04.002
ORGELE 4038
DOI:
Reference:
To appear in: Organic Electronics
Received Date: 5 January 2017
Revised Date: 27 March 2017
Accepted Date: 1 April 2017
Please cite this article as: X. Gao, Y. Zhang, C. Fang, X. Cai, B. Hu, G. Tu, Efficient deep-red
electroluminescent donor-acceptor copolymers based on 6,7-dichloroquinoxaline, Organic Electronics
(2017), doi: 10.1016/j.orgel.2017.04.002.
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C8H17
O
OC8H17
1.0
0.8
0.6
0.4
0.2
0.0
PClQ3T
N
N
C6H13
C6H13
*
S
S
Cl
Cl
S
*
n
400
600
800
Wavelength ( nm )

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Efficient Deep-Red Electroluminescent Donor-Acceptor Copolymers Based on
6,7-Dichloroquinoxaline
Xiang Gao,a Yubao Zhang,b Cheng Fang,a Xiang Cai,c Bin Huc, d* and Guoli Tuc*
a School of Materials Science & Engineering, Wuhan Institute of Technology, Wuhan
430073, China
b Jiangxi Engineering Laboratory for Optoelectronics Testing Technology, Nachang
Hangkong University, Nanchang 330063, China
c Wuhan National Laboratory for Optoelectronics, Huazhong University of Science
and Technology, Wuhan, Hubei 430074, China
d Department of Materials Science and Engineering, University of Tennessee,
Knoxville, TN 37996, USA

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Abstract
Since the large steric hindrance caused by chlorine atoms not only suppresses the
aggregation but also results in large stokes shift and low self-absorption, a series of
donor-acceptor alternating copolymers based on 6,7-dichloroquinoxaline have been
synthesized by modifying the structures of oligothiophenes. All the polymers have
been well characterized to study the effects of the length of oligothiophenes and the
steric hindrance on the optical, electronic and electroluminescent properties. It was
observed that the intramolecular charge transfer absorption was weakened by steric
hindrance. Unlike non-chloride analogues, prolonged conjugated length resulted in
smaller bandgap, given similar steric hindrance. Deep-red emission centered at 678
nm with brightness about 1800 cd m-2 was achieved with external quantum efficiency
1.34% using dopant/host technic.
Keywords
conjugated copolymers; deep-red electroluminescent materials; chlorine-bearing
polymers; polymeric light-emitting diodes (PLED)
1. Introduction
Conjugated polymers have drawn particular attentions due to their applications in
polymeric light-emitting diodes (PLEDs),1-4 organic photovoltaic devices (OPVs)5,6
and organic field effect transistors (OFETs),7,8 which can be fabricated conveniently
by solution processing toward low cost and flexible products. Among various

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conjugated polymers, halide ones exhibit special properties. Polymers containing
fluorine atoms9-15 on the backbone were demonstrated to be effective to tune the
energy levels, packing behaviors and phase separation behaviors of the materials,
resulting in better device performances and improved stability than fluorine-free
analogues in OFETs and OPVs. Additionally, the effects of bromine end-group,
residues after polycondensation, have also been well studied. Br end-group has been
confirmed harmful to the efficiency of devices,16-19 and end-capping is widely used to
enhance the quality of conjugated polymers and efficiency of OPVs and PLEDs.20-24
In the last few years, brominate side chain was used to design photocrosslinkable
conjugated polymers to enhance the thermal stability of OPV devices.25-30 But there
are only few papers31-35 reported chlorine-bearing conjugated polymers because of the
difficulties in controlling the chlorinated ratio and position and yielding high
molecular weight and regioregularity.36-39
Lately, our group systematically studied the method of synthesizing
chlorine-containing conjugated polymers and the effects of chlorine atoms on the
properties of these chlorine-containing conjugated polymers.32-35 Stille reaction was
competent for straight synthesizing chlorine-bearing donor-acceptor alternating
conjugated copolymers when the electron density of the chlorine-bearing acceptor
monomers were not too low, such as 2,3-dis(3-(octyloxy)phenyl)quinoxaline.33 And
deeper frontier orbital levels were observed in these chlorine-bearing polymers.33-35
While Suzuki reaction was appropriate for strong electron-withdrawing moieties, such
as benzo[c][1,2,5]thiadiazole, and higher frontier orbital levels were observed in these

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copolymers.33 We find that chlorine-containing polymers are promising red to
near-infrared electroluminescent conjugated polymers. All chlorine-containing
polymers exhibit large stokes shift and low self-absorption, which is favorable for
photoluminescence and electroluminescence. This may be ascribed to the large
covalent radius of chlorine atom which is 102 p, large enough to suppresses the
aggregation and inhibit the formation of semiquinoid geometry.34,35
Although deep-red electroluminescent materials are vital for display, reports
about deep-red emitting conjugated polymers are still rare expect those containing
selenium atoms.40,41 In this contribution, 3,3'-dihexyl-2,2'-bithiophene and
3,3''-dihexyl-2,2':5',2''-terthiophene were used as the donor moieties to copolymerized
with 6,7-dichloroquinoxaline to finely modify the electroluminescent (EL) properties.
Deep-red emission centered at 678 nm with brightness about 1800 cd m-2 was
achieved with highest external quantum efficiency of 1.34% using dopant/host technic.
The EL properties of PClQ2T34 were also characterized to study the steric effect of
alkyl sidechain. Compared with PClQT and PClQ4T,35 the effects of the number of
thiophene and the steric hindrance in oligothiophenes were also discussed.
2. Experiment section
2.1 General Information
All reagents and chemicals were purchased from commercial sources (Aldrich,
Acros, TCI) and used without further purification. Tetrahydrofuran (THF) were
distilled from Na/benzophenone prior to use. Gel permeation chromatography (GPC)

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measurements were performed on a Polymer Laboratories GPC-50 instrument using
THF as the eluent at 40 °C. The obtained molecular weight is relative to the
polystyrene standard. The content of S and Cl was determined by combustion titration
method in Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences.
Thermogravimetric analysis was performed on a PerkinElmer Pyris1 TGA under N2
1
atmosphere with the heating-up rate of 10 °C min-1. H nuclear magnetic resonance
(NMR) measurements were carried out with a recorded Bruker 400 MHz DRX
spectrometer. UV-Visible (UV-Vis) absorption spectra were recorded in dilute
chloroform solutions or in films by a Shimadzu UV-3600 spectrophotometer.
Fluorescence spectra were carried out with an Edinburg PLS 920. The transient
photoluminescence measurements were also carried out with Edinburg PLS 920 using
light-emitting diode laser (λ = 367.4 nm) as the excitation source. The measurement
of absolute photoluminescence quantum yield of thin films was performed on Hitachi
F-7000 equipped with integrating sphere. The excitation wavelengths were 459 nm
and 519 nm for PClQ2HT and PClQ3T films respectively. The measurements of
absolute photoluminescence quantum yield of thin films were performed three times
independently. Thin films for the measurements were spun coated onto precleaned
quartz slides from solutions with a concentration of 5 mg mL-1. Cyclic Voltammetry
(CV) measurements were performed using standard three-electrode electrochemical
cell in a 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF6) in acetonitrile
solution at room temperature with a scanning rate of 50 mV s-1. During the CV
measurements, a carbon working electrode coated with a thin layer of copolymers, a

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platinum wire as the counter electrode, and a silver wire as the quasi-reference
electrode were used. The potential of Ag/AgNO3 reference electrode which has a
reduction potential of -4.8 eV was internally calibrated by using the
ferrocene/ferrocenium redox couple (Fc/Fc+).
2.2 Synthesis
2,5-bistrimethyltinthiophene
(1)
and
5,8-dibromo-6,7-dichloro-2,3-bis(3-
(octyloxy)phenyl) quinoxaline (6) were synthesized according to the reference 35.
3,3''-dihexyl-2,2':5',2''-terthiophene (2) was synthesized following standard Stille
reaction. 5,5''-bis(trimethylstannyl)-3,3''-dihexyl-2,2':5',2''-terthiophene (3), and
5,5'-bis(trimethylstannyl)-3,3'-dihexyl-2,2'-bithiophene (5) were synthesized similar
to the procedure of synthesizing compound 1. All the polymers were synthesized
according to references 35. The synthetic routs are shown in Scheme 1. The NMR and
EA data of the monomers and the copolymers are listed below.
1
5,5''-bis(trimethylstannyl)-3,3''-dihexyl-2,2':5',2''-terthiophene (3): H-NMR (400
MHz, CDCl3, δ): 7.18 (d, 2H, J = 5.2 Hz), 7.06 (s, 2H), 6.95 (d, 2H, J = 5.2 Hz), 2.79
(t, 4H, J = 8.0 Hz), 1.96-1.62 (m, 4H), 1.40-1.26 (m, 12H), 0.89 (t, 3H, J = 6.8 Hz).
3,3'-dihexyl-2,2'-bithiophene (4): Bis(triphenylphosphine)nickel(II) dichloride
(1.31 g, 2 mmol), triphenylphosphane (1.04 g, 4 mmol), zinc powder (1.31 g, 20
mmol) and KI (83 mg, 0.5 mmol) were added into anhydrous THF under nitrogen
atmosphere. The mixture was stirred at room temperature for 0.5 h. The colour
became reddish brown. Then 2-bromide-3-hexylthiophene (4.94 g, 20 mmol) was
added. The mixture was refluxed overnight. The mixture was extracted with ethyl

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acetate. The crude product was purified by column chromatography with hexane as
the eluent. Pure product as colourless transparent oil was obtained (2.08 g, 80.78%).
1H NMR (400 MHz, CDCl3, δ): 7.31 (d, 2H, J = 5.2 Hz), 6.98 (d, 2H, J = 5.2 Hz),
2.52 (t, 4H, J = 8 Hz), 1.56 (m, 4H), 1.31-1.22 (m, 12H), 0.87 (t, 6H, J = 6.8 Hz).
1
5,5'-bis(trimethylstannyl)-3,3'-dihexyl-2,2'-bithiophene (5): H NMR (400 MHz,
CDCl3, δ): 7.02 (s, 1H), 2.51 (t, 4H, J = 8 Hz), 1.57-1.54 (m, 4H), 1.30-1.24 (m, 12H),
0.90-0.78 (m, 6H), 0.43 (s, 18H).
PClQ2HT: The hexane fraction was precipitated in methanol. Finally, the polymer
was collected by filtration and dried under vacuum at 40 °C overnight (216 mgꢀ
1
92.39%). Mn = 17.9 k, PDI = 2.07. H NMR (400 MHz, CDCl3, δ): 7.49 (s, 2H),
7.23-7.14 (m, 6H), 6.84 (d, 2H, J = 8 Hz), 3.71 (b, 4H), 2.78 (b, 4H), 1.70 (b, 4H),
1.54-1.51 (m, 4H), 1.36-1.16 (b, 32H), 0.89-0.81 (m, 12Hz). Element analysis:
Theory: Cl 7.55, S 6.81 (%); Found: Cl 7.79, S 6.72 (%).
PClQ3T: The chloroform fraction was precipitated in methanol. Finally, the
polymer was collected by filtration and dried under vacuum at 40 °C overnight (401.2
mg, 78.59%). Mn = 19.3 k， PDI = 1.54. 1H NMR (400 MHz, CDCl3, δ): 7.46 (b, 2H),
7.35 (b, 2H), 7.26 (b, 4H), 7.18 (d, 4H, J = 4.8 Hz), 6.90 (b, 2H), 3.80 (t, 4H, J = 6.0
Hz), 2.95 (t, 4H, J = 8 Hz), 1.82 (t, 4H, J = 6.8 Hz), 1.61 (m, 4H), 1.51 (m, 4H),
1.39-1.33 (m, 12 H), 1.23-1.22 (b, 16H), 0.91 (t, 6H, J = 6.8 Hz), 0.82 (t, 6H, J = 6.8
Hz)。Element analysis: Theory: S 9.39, Cl 6.95 (%); Found: S 9.38, Cl 6.61 (%).
2.3 Device fabrication and characterization

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The fabrication process followed a standard procedure. PEDOT:PSS (Bayton
P4083, Bayer AG) was spin-coated on a pre-cleaned and plasma treated ITO glass and
dried in an oven at 120 °C for 30 min. The thickness of this layer was about 30 nm.
Then PClQ2HT and PClQ3T were spin-coated with a concentration of 10 mg mL-1 in
chloroform and PClQ2T was spin-coated with a concentration of 10 mg mL-1 in
o-dichlorobenzene. The doped films were spin-coated with a concentration of 15 mg
mL-1 host material, green-emitting materials F8BT, in o-dichlorobenzene with
different doping ratio. The thickness of light-emitting layers were about 90-100 nm.
Finally 20 nm Ca and 100 nm Al were subsequently deposited through mask (defined
active area of 0.09 cm2) in a chamber at pressure of 10-4 Pa. The thicknesses of Ca and
Al were monitored during deposition by using a thickness monitor. And the
thicknesses of the PEDOT:PSS and polymer layers were estimated by Surface Profiler
(Veeco dektak 150). Characterization of the PLEDs was measured with a diode array
rapid scan system using a PhotoResearch PR655 spectrophotometer and a
computer-controlled, programmable, direct current (DC) source. The response range
of PR655 ends at 780 nm. Additionally, hole-only devices and electron devices were
also fabricated with the configuration as ITO/PEDOT:PSS/Polymers/MoO3/Ag and
ITO/ZnO/Polymers/Ca/Ag, respectively. Colloidal ZnO nanocrystals in electron-only
devices were synthesized by a low-temperature solution-precipitation method as
described in reference.42
3. Results and discussion
3.1 Synthesis and thermastability

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When the number of thiophene ring in the oligothiophene increases to 2, the
resulted polymer PClQ2T exhibited limited solubility in hot toluene,34 alkyl side
chains were introduced to the 3,3' position in 2,2'-bithiophene to enhance the
solubility, namely PClQ2HT, the number-average-molecular weight of which is 17.9 k.
PClQ2HT exhibits super well solubility even in hexane. PClQ3T also exhibits good
solubility in common organic solvent at room temperature, such as chloroform, THF
and toluene. Similar with the analogues, the chlorine atoms were well preserved and
no cross-linking happened in the synthetic procedure which was confirmed by the 1H
NMR and element analysis data, as listed in experiment part and Table 1. At 258 °C,
PClQ2HT has lost 1 w%, while PClQ3T didn’t loss 1 w% until 430 °C. The
decomposition temperature determined by 5 w% for PClQ2HT and PClQ3T are 409
and 446 °C respectively. Compared with other conjugated copolymers using
6,7-dichloroquinoxaline as the acceptor moiety,34,35 this abnormal instability of
PClQ2HT might be attributed to the huge steric effect in PClQ2HT as proved by the
absorption spectra and the results of Density Functional Theory (DFT) calculations.
3.2 Absorption and fluorescence
The UV-Vis absorption spectra of PClQ2HT and PClQ3T in chloroform and in thin
films were shown in figure 1. PClQ2HT and PClQ3T present two absorption bands as
other typical donor-acceptor alternating copolymers. The peak at short wavelength
could be assigned to π-π* transition and the absorption in low energy region is
originated from its intramolecular charge-transfer. Comparing the absorption spectra
of this series of polymers based on 6,7-Dichloroquinoxaline, the π-π* transition

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bathochromic shifts notably as the length of oligothiophene increases except
PClQ2HT, while the low energy peaks of PClQ2T, PClQ3T and PClQ4T only shift
several nanometers. This is similar to the nonchloride analogues.43 But the red-shifts
of the fluorescent peaks can’t be negligible until the number of the oligothiophene
increases to 3. This phenomenon is different from that in the alternating
quinoxaline/oligothiophene copolymers.43 The absorption spectra of PClQ2HT are
almost the same as that of PClQT and is an exception of the rules concluded above,
which might be attributed to the steric effect of the hexyl at 3,3' position in
2,2'-bithiophene. This will be discussed in detail in the “Simulation” section. The
PClQ2HT films exhibited pure red-emission with the peak located at 632 nm. All the
chloride polymers exhibit larger Stokes shift and weaker self-absorption, especially a
large Stokes shift about 200 nm is realized in the PClQ3T and PClQ4T35 films. This is
because the steric hindrance of chlorine atoms reduce the ability to form planar
semiquinoid states.44 The average absolute photoluminescence quantum yields of
PClQ2HT and PClQ3T in thin films are 12.5% and 6.1% respectively, as listed in
Table 2. This decrease may be ascribed to an intrinsic limitation of narrower bandgap
of PClQ3T according to the energy-gap law and higher content of sulfur atoms.
Transient photoluminescence measurements exhibit that there is only one lifetime in
the order of nano-second for both PClQ2TH and PClQ3T in solution or in films, as
listed in Table 2, indicating that PClQ2TH and PClQ3T are fluorescent materials.
3.2 Charge Mobility

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The hole and electron mobility of PClQ2HT and PClQ3T were evaluated based on
the space-charge-limited current method in hole-only and electron-only devices with
the
configuration
ITO/PEDOT:PSS/Polymers/MoO3/Ag
and
ITO/ZnO/Polymers/Ca/Ag respectively. The results are listed in Table 1. PClQ2HT
and PClQ3T exhibit similar hole mobility, which are 1.73×10-6 cm2 V-1 S-1 and
2.21×10-6 cm2 V-1 S-1, respectively. While the electron mobility of PClQ2HT
(1.88×10-7 cm2 V-1 S-1) is one magnitude higher than that of PClQ3T (2.72×10-8 cm2
V-1 S-1). This may be ascribed to the higher content of chlorine atoms in PClQ2HT.45
3.3 Calculation and energy levels
The HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied
molecular orbital) levels of PClQ2HT and PClQ3T estimated from their CV
measurement were listed in Table 1. The LUMO levels of PClQ2HT and PClQ3T
locate around -3.40 eV similar like other chlorine-bearing copolymers.34,35 The
HOMO levels are-5.77 eV and -5.49 eV, respectively.
DFT calculations were carried out using ADF.2009.01 software at the
LDA+GGA+METAGGA/DZP level taking one repeat unit as model with trunked
alkyl chains. Fig. 2 showed the electron density distributions of the HOMO and
LUMO energy levels of the chloride polymers. In all conditions, the chlorine atoms
resulted in the located LUMO levels on the quinoxaline ring. This is consistent with
the phenomenon that the LUMO levels of these chlorine-bearing polymers are almost
the same. On the other hand, the HOMO levels of PClQ3T centered on the donor
moieties, i.e. terthiophene. And the HOMO levels of PClQ2HT distributed along the

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conjugated chain. Therefore, increasing the thiophene number causes elevated HOMO
level of PClQ3T, which matches the results of CV measurement. The HOMO level of
PClQ3T is about 0.3 eV higher than that of PClQ2HT. Additionally, the notable steric
hindrance of chlorine atoms reduced the planarity along the polymer backbone and
suppressed the intermolecular stacking in films. The dihedral angles between
quinoxaline ring and thiophene in PClQ2HT and PClQ3T are 44.8° and 73.6°
respectively, which is much larger than that of non-chloride polymer, 14.2°.35 As for
PClQ2HT, the dihedral angle in bithiophene moiety is so large that the absorption
spectrum is almost the same as that of PClQT34 although the number of thiophene
increases. Additionally, this large dihedral angle, namely large steric hindrance in
PClQ2HT, can also explain why the absorption spectrum of PClQ2HT in thin film
only slightly red-shifted compared with that of PClQ2HT in solution.
3.4 Electroluminescent properties
Non-doped PLEDs of PClQ2T, PClQ2HT and PClQ3T with configuration of
ITO/PEDOT:PSS/Polymer/Ca/Al were well characterized. The EL spectra of these
single layer devices were exhibited in Figure 3, and the main EL properties of these
copolymers containing 6,7-dichloroquinoxaline are listed in Table 3. Although
PClQ2HT exhibits saturate red-emission peaking at 636 nm with the CIE coordinate
(0.62, 0.38), the brightness and external quantum efficiency are quite low. The turn-on
voltage of PLEDs based on PClQ2HT is much higher than that of PClQ3T. Given that
the hole mobility and LUMO levels of PClQ2HT and PClQ3T are almost the same,
the reason might be ascribed to the high hole injection barrier in PLEDs based on

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PClQ2HT, the HOMO level of which (-5.77 eV) is much deeper than that of PClQ3T
(-5.49 eV). The EL spectra peaks red shifted as the number of thiophene increased
expect PClQ2HT as listed in Table 3. This is because of the steric hindrance of alkyl
chain at the 3,3’ position in the bithiophene moiety in PClQ2HT as described in
Calculation part. PClQ2T and PClQ3T exhibits deep-red to near-infrared emission
with the EL peaks at 672 nm and 708 nm respectively.
It has been proved it’s useful to use high efficient green-emitting conjugated
polymer F8BT as host material to improve the performance of deep red to NIR light
emitting materials.35,43,46 As proved by the photophysical characterization, all these
polymers are fluorescent materials, only singlet exciton can be used. Because well
overlap between the PL spectrum of F8BT and the absorption spectra of
PClQ2T/PClQ3T, efficient Förster energy transfer can be expected. Additionally, the
HOMO and LUMO levels of PClQ2T, PClQ2HT and PClQ3T located between those
of F8BT, trapping of injected charges were also expected, but only the blends of
PClQ3T/F8BT showed complete charge transfer in PLEDs. The reason for incomplete
charge transfer in the blends of PClQ2T/F8BT might be too strong aggregation.34
While the reason for PClQ2HT/F8BT might be ascribed to similar frontier orbital
energy levels of PClQ2HT and F8BT and finite overlap between the PL spectrum of
F8BT and the absorption spectrum of PClQ2HT. The EL performance properties of
PClQ3T in host/guest system were listed in Table 3. The current
density-voltage-luminance characteristics and PL/EL spectra of PClQ3T in host/guest
system were exhibited in Figure 4a and Figure 4b respectively. The EL peaks of these

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host/guest systems red shifted as the contents of PClQ3T increased in company with
lower efficiency. This is similar with the trend in host/guest system using small
molecule DCM2 as red light-emitting materials.47 Finally deep-red emission centered
at 678 nm with brightness about 1800 cd m-2 were achieved with EQE as 1.34%,
which is much higher than deep-red emitting conjugated materials based on
4,7-diselenophen-2ꢁ-yl-2,1,3-benzothiadiazole41 or naphthoselenadiazole40.
4. Conclusion
In this series of copolymers using 6,7-dichloroquinoxaline as the acceptor moieties,
the HOMO levels increase and electroluminescent peaks red shift as the number of
thiophene in donor moieties increases considering comparable steric hindrance, while
the photoluminescent peaks red shift slightly when the number of thiophene is larger
than 3. PClQ2HT exhibited similar properties as that of PClQT because of huge steric
hindrance. Finally deep-red emission centered at 678 nm with brightness about 1800
cd m-2 were achieved with EQE as 1.34% using PClQ3T as the guest emitter blended
with high-efficiency green-emitting polymer F8BT. This indicates that
6,7-dichloroquinoxaline is an useful acceptor moiety to construct efficient deep-red
electroluminescent materials.
Acknowledgements:
The authors acknowledge the financial supports from National Significant
Program (2014CB643506 and 2013CB922104), the National Natural Science

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Foundation of China (NSFC 21274048 and 61475051), and science foundation of
Wuhan Institute of Technology (k201629).
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ACCEPTED MANUSCRIPT
C6H13 C6H13
S
1) -78 oC, n-BuLi;
Pd2(dba)3, P(o-Tol)3
reflux, overnight
S
S
S
Me3Sn
Br
Br
Br
SnMe3
+
2) Me3SnCl, -78 oC;
3) r.t. overnight
S
S
C6H13
2
1
S
1) -78 oC, n-BuLi;
S
Me3Sn
SnMe3
S
C6H13
3
2) Me3SnCl, -78 oC;
3) r.t. overnight
C6H13
C6H13
C6H13
1) ice-salt bath, n-BuLi,
30 min; r.t. 30 min
Me3Sn
Zn, Ni(PPh3)2Cl2, KI, PPh3
THF, reflux
S
S
S
Br
S
S
2) Me3SnCl, ice-salt bath, 1 h
3) r.t. overnight
SnMe3
C6H13
C6H13
C6H13
4
5
C8H17
Pd2(dab)3 , P(o-Tol)3
toluene, reflux
O
OC8H17
C8H17O
OC8H17
Me3Sn
C6H13
S
N
N
+
N
N
C6H13
S
S
SnMe3
*
Br
Br
C6H13
S
Cl
Cl
*
Cl
Cl
n
C6H13
6
5
PClQ2HT
C8H17O
OC8H17
C8H17
Pd2(dab)3 , P(o-Tol)3
toluene, reflux
O
OC8H17
S
S
Me3Sn
N
N
SnMe3
N
N
+
S
C6H13
S
C6H13
Br
Br
*
C6H13
C6H13
S
Cl
Cl
Cl
Cl
S
*
n
6
3
PClQ3T
C8H17O
OC8H17
OC8H17
OC8H17 C8H17
O
C8H17O
N
N
N
N
N
N
*
C6H13
S
n
*
S
S
S
n
S
Cl
Cl
Cl
Cl
Cl
Cl
S
S
*
n
PClQT
PClQ2T
PClQ4T
C6H13
Scheme 1. Routes to synthesize the conjugated polymers.

ACCEPTED MANUSCRIPT
1.0
0.8
0.6
0.4
0.2
0.0
400
600
800
Wavelength ( nm )
Figure 1. Normalized UV-Vis absorption spectra of PClQ2HT (square) and PClQ3T
(circle) in chloroform solution (hollow symbol) and in films (filled symbol), and
normalized fluorescent spectra of PClQ2HT, PClQ3T and F8BT (triangle) in films
(half-filled symbol).

ACCEPTED MANUSCRIPT
Figure 2.Geometry and frontier molecular orbitals for model compounds of PClQ2HT,
and PClQ3T.

ACCEPTED MANUSCRIPT
1.0
0.8
0.6
0.4
0.2
0.0
PClQ2HT
PClQ2T
PClQ3T
400
600
Wavelength (nm)
Figure 3. Electroluminescent spectra of PLEDs based on PClQ2HT (square), PClQ2T
(circle) and PClQ3T (triangle) with the configuration ITO/PEDOT:PSS/Polymer/Ca/
Al.

ACCEPTED MANUSCRIPT
1200
1000
800
600
400
200
0
a
103
102
101
100
PClQ3T
5% PClQ3T
10% PClQ3T
15% PClQ3T
0
1
2
3
4
V(V)
5
6
7
8
9
1.0
0.8
0.6
0.4
0.2
0.0
1.0
0.8
0.6
0.4
0.2
0.0
b
PClQ3T
5% PClQ3T
10% PClQ3T
15% PClQ3T
300
400
500
600
700
800
（
）
Wavelenghth nm
Figure 4 a) Current density-voltage-luminance (J-V-L) characteristics of PClQ3T
based host/guest system PLEDs with different doping ratio. b) Photoluminescence
(filled symbol) and electroluminescence (hollow symbol) pectra of PClQ3T and
PClQ3T/F8BT blends/PLEDs. Down triangle: pure PClQ3T; Squre: 5w% PClQ3T in
F8BT; Up triangle: 10w% in F8BT; Circle: 15 wt% PClQ3T in F8BT.

ACCEPTED MANUSCRIPT
Table 1. Polymerization results, energy levels and charge mobility of polymers
Mobility (cm2 V-1 s-1)
Td (°C)
HOMO
LUMO
Eg
ꢀe
ꢀh
1 w%
5 w%
(eV)
(eV)
(eV)
PClQ2HT
PClQ3T
258
430
409
446
-5.77
-5.49
-3.39
-3.40
2.38
2.09
1.88×10-7
2.72×10-8
1.73×10-6
2.21×10-6
Table 2. Optical properties of polymers
λabs (nm)
τ (ns)
λemia (nm)
Φa (%)
Solution
306, 390, 445b
368, 480
Film
Solution
2.10
Film
1.86
1.96
PClQ2HT
PClQ3T
308, 402, 460b
366, 518
632
704
12.5±0.2
6.1±0.5
1.95
a in thin films; b shoulder peak

ACCEPTED MANUSCRIPT
Table 3 Electroluminescent properties of the polymers
Blend ratio Von
Brightness
(cd m-2)c
124.9
254.7
16.4
λmax
(nm)d
620
672
636
708
672
678
740
692
EQE
(%)c
0.21
0.12
0.04
0.39
1.09
1.34
0.32
0.45
CIE (x, y)d
ref
41
(w%)a
(V)b
6.2
3.1
8.0
3.3
2.8
3.1
5.0
4.2
PClQT
PClQ2T
PClQ2HT
0
0
(0.60, 0.40)
(0.68, 0.32)
(0.62, 0.38)
(0.71, 0.29)
(0.65, 0.35)
(0.66, 0.34)
(0.71, 0.29)
(0.67, 0.32)
0
this
0
62.6
work
PClQ3T
10
15
0
1985
1806
23.5
PClQ4T
41
10
1493
a the weight ratio of copolymers to F8BT b Turn-on voltage at the brightness of 1.0 cd
m-2 c The maximum value. d At the maximum external quantum efficiency.

ACCEPTED MANUSCRIPT
1. chlorine-bearing conjugated polymers exhibit unique properties;
2. revealing the structure-property relationship of chlorine-bearing polymers;
3. efficient deep-red electroluminescent materials.