Perylene diimide copolymers with dithienothiophene and dithienopyrrole: Use in n-channel and ambipolar field-effect transistors

Article abstract of DOI:10.1002/pola.26521

Solution-processable polymers consisting of perylene diimide (PDI) acceptor moieties alternating with dithienothiophene (DTT), N-dodecyl-dithienopyrrole (DTP), or oligomers of these donor groups have been synthesized. We have, in addition to varying the d

Full text of DOI:10.1002/pola.26521

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Perylene Diimide Copolymers with Dithienothiophene and
Dithienopyrrole: Use in n-Channel and Ambipolar Field-Effect Transistors
Shiming Zhang,1 Yugeng Wen,1 Weiyi Zhou,1 Yunlong Guo,1 Lanchao Ma,1 Xingang Zhao,1
Zhen Zhao,1 Stephen Barlow,2,3 Seth R. Marder,2,3 Yunqi Liu,1 Xiaowei Zhan1,4
1Beijing National Laboratory for Molecular Sciences and CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese
Academy of Sciences, Beijing 100190, China
2School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332
3Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, Georgia 30332
4Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, China
Correspondence to: X. Zhan (E-mail: xwzhan@iccas.ac.cn)
Received 5 September 2012; accepted 3 December 2012; published online
DOI: 10.1002/pola.26521
ABSTRACT: Solution-processable polymers consisting of pery-
lene diimide (PDI) acceptor moieties alternating with dithieno-
thiophene (DTT), N-dodecyl-dithienopyrrole (DTP), or
oligomers of these donor groups have been synthesized. We
have, in addition to varying the donor, varied the N,N0 sub-
stituents of the PDIs. The thermal, optical, electrochemical,
and charge-transport properties of the polymers have been
investigated. The polymers show broad absorption extending
from 300 to 1000 nm with optical band gaps as low as 1.2 eV;
the band gap decreases with increasing the conjugation
length of donor block, or by replacement of DTT by DTP. The
electron affinities of the polymers, estimated from electro-
chemical data, range from ꢀ3.87 to ꢀ4.01 eV and are slightly
affected by the specific choice of donor moiety, while the esti-
mated ionization potentials (ꢀ5.31 to ꢀ5.92 eV) are more sen-
sitive to the choice of donor. Bottom-gate top-contact organic
field-effect transistors based on the polymers generally ex-
hibit n-channel behavior with electron mobilities as high as
1.7 ꢁ 10–2 cm2/V/s and on/off ratios as high as 106; one PDI-
DTP polymer is an ambipolar transport material with electron
mobility of 4 ꢁ 10–4 cm2/V/s and hole mobility of 4 ꢁ 10–5
cm2/V/s in air. There is considerable variation in the charge
transport properties of the polymers with the chemical struc-
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tures. 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym
Chem 000: 000–000, 2013
KEYWORDS: conjugated polymers; charge transport; structure-
property relations; field-effect transistor; perylene diimide
INTRODUCTION Organic electron-transport (ET) materials
are essential for the fabrication of organic p-n junctions, pho-
tovoltaic cells, n-channel field-effect transistors (OFETs), and
complementary logic circuits. High-performance ET materials
must have high electron affinity to facilitate electron injec-
tion from electrodes in OFETs, good intermolecular elec-
tronic orbital overlap to facilitate high mobility, and good air
stability, ideally both as neutral materials and under device
operating conditions.1 Good ET materials include acenes and
oligothiophenes bearing electron-withdrawing substituents,
such as fluoro, cyano, or acyl, fullerenes, and rylene and
acene tetracarboxylic diimides.1 In general, development of
high-performance (stable, high-mobility) organic ET materi-
als has lagged behind that of hole-transport (HT) materials.
In particular, high-mobility n-type polymers remain rare.2
Ambipolar OFETs, that is, OFETs based on materials that can
function as either ET or HT materials depending on the gate
voltage, are important for complementary inverters that ena-
ble robust, low-power circuits with wide noise margins with-
out using advanced patterning techniques to selectively de-
posit separate ET and HT materials.1(c) Some single-
component organic materials exhibit ambipolar transport
properties.3 In particular, a few diketopyrrolopyrrole (DPP)-
based polymers exhibit excellent ambipolar transport prop-
erties with both electron and hole mobilities as high as 1
cm2/V/s in nitrogen.4 However, air-stable ambipolar organic
semiconductors remain very rare. Usta and Facchetti
reported the first air-stable ambipolar OFET polymer based
on indenofluorenebis(dicyanovinylene) core and having both
electron and hole mobilities of about 2 ꢁ 10ꢀ4 cm2/V/s.5
Perylene-3,4:9,10-tetracarboxydiimides (PDIs) are a robust,
versatile class of materials with excellent stability, high elec-
tron affinities and, in some cases, high electron mobilities;
they are, therefore, promising candidates for a variety of or-
ganic electronics applications.6 For example, OFETs based on
PDI thin films and single crystals exhibited electron mobili-
ties as high as 1–6 cm2/V/s in vacuum and in air.7 However,
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FIGURE 1 Chemical structures of PDI copolymers which is discussed in this article.
high-mobility PDI polymers remain rare. Several n-type con-
jugated polymers based PDI have been synthesized and used
in n-channel OFETs and polymer solar cells.8 We reported
the synthesis of the first soluble PDI-based fully conjugated
polymer; this PDI-dithienothiophene (DTT) copolymer (1a,
Fig. 1) exhibited a saturation electron mobility of 1.3 ꢁ 10–2
cm2/V/s and a low threshold voltage of 4 V in nitrogen.8(a)
Later, a dithienopyrrole (DTP) analogue, 2a, was reported to
show an electron mobility of 1.2 ꢁ 10–3 cm2/V/s on anneal-
ing at 100 ꢂC for 60 min under inert atmosphere.8(b) Fac-
chetti and coworkers have reported a PDI-bithiophene copol-
ymer with a mobility of 2 ꢁ 10–3 cm2/V/s in vacuum.8(g)
Thelakkat and coworkers have reported a polymer contain-
ing PDIs as pendant groups with a mobility of 1.2 ꢁ 10–3
cm2/V/s under inert atmosphere after thermal annealing at
thiophene donor linkers, and the N-alkyl substituents. In
addition to comparing OFET behavior, we also compare the
optical and electrochemical properties of these polymers.
RESULTS AND DISCUSSION
Synthesis and Characterization
Polymers 1a, 2a, and 3a were synthesized according to our
previously published procedures.8(a,b) The synthetic routes to
the remaining polymers are outlined in Scheme 1. 1,7-Dibro-
moperylene-3,4:9,10-tetracarboxylic dianhydride10 was con-
densed with the amines to yield the new N,N0-disubstituted
1,7-dibromoperylene-3,4:9,10-tetracarboxylic diimides (Ia-b)
in 24–64% yields. The Stille coupling reaction between 2,6-
distannyl DTT or DTP derivatives and Ia-c or a 1,7-bis(-
bromo-DTT) PDI in the presence of a catalytic amount of
Pd(PPh3)4 afforded the new copolymers 1b-c, 2b, and 3b in
87–91% yields.
9
ꢂ
210 C for 60 min.
In this article, we compare the OFET behavior of a series of
low band gap p-conjugated copolymers of PDI acceptors
with DTT and DTP donors (Fig. 1), including the previously
reported 1a and 2a, an additional polymer, 3a, that we have
previously examined as an electron acceptor for all-polymer
solar cells,8(b) and four new polymers. One of these materials
shows stable ambipolar OFET behavior in air, while some of
the other polymers show good n-channel OFET performance
for solution-processed materials. As shown in Figure 1,
within this series, we vary the number and nature of fused
All these polymers have good solubility in chloroform. Molec-
ular weights of the polymers were determined by gel perme-
ation chromatography (GPC) using polystyrene standards as
calibrants with toluene as eluant. Table 1 shows the mole-
cule weights of the polymers as well as their thermal prop-
erty. All the polymers except 1b (not measured due to poor
solubility in toluene) exhibit weight-average molecular
weight (Mw) of 16,000–82,000 with polydispersity index
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SCHEME 1 Synthesis of the polymers.
(Mw/Mn) of 1.5–1.8. All the polymers exhibit good thermal
stability with decomposition temperatures (Td) of 330–
430ꢂC, as estimated by thermogravimetric analysis (TGA)
(Table 1).
reduction potentials, assuming the absolute energy level of
þ/0
FeCp2
to be 4.8 eV below vacuum. As we have previously
discussed for 1a, 2a, and 3a, the estimated EAs are relatively
insensitive to the choice of donor groups. The data for the
new polymers are consistent with this picture and also show
that, consistent with data for small-molecule PDIs,12 the
choice of N,N0-substituents does not significantly affect the
EAs either (Table 3). The estimated IPs are relatively insensi-
tive to the choice of N,N0-substituents. However, the esti-
mated IPs decrease with increasing the number of DTT units
or replacing DTT by DTP. The optical band gaps (Egopt) are
relatively insensitive to the choice of N,N0-substituents, while
decrease with increasing the number of DTT units or replac-
ing DTT by DTP. The trend in IP-EA gaps (Egec) obtained
Absorption Spectra
UV-vis-NIR absorption spectra of the polymers in chloroform
are shown in Figure 2(a) with the maxima summarized in
Table 2. We have previously assigned the lowest energy
bands of 1a, 2a, and 3a to transitions with substantial do-
nor-to-acceptor charge-transfer character, and suggested that
the two strong higher energy bands are primarily PDI-based
and donor-based (with overlap between these two transi-
tions in the case of 3a).8(b),11 The spectra of 1b–c and 2b
are similar to those of 1a and 2a, respectively, indicating
that the N,N0-substituents on the PDI have only minor effects
on the spectra, as is also seen in the case of small-molecule
PDIs.12 In the case of 3b, both bands are significantly red-
shifted relative to those of 3a; the shift of the charge-trans-
fer-type band can be attributed to the greater donor strength
of DTP vs. DTT.8(b),13,14 The UV-vis-NIR absorption spectra of
the polymers in thin films are shown in Figure 2(b) and are
generally similar to the solution spectra, with only minor red
or blue shifts in the absorption maxima being observed.
ec
from electrochemistry is similar to Egopt. However, Eg is
TABLE 1 Molecular Weights and Thermal Properties of the
Polymers
a
a
a
c
Polymer
Yield (%)
Mn
Mw
Mw/Mn
Td (ꢂC)
b
1b
1c
2b
3b
a
88
87
89
91
–
–
–
334
422
342
426
25,000
44,800
9,400
38,000
82,300
16,000
1.5
1.8
1.7
Electrochemistry
To estimate the solid-state ionization potential (IP) and elec-
tron affinity (EA) of the polymers, we studied their electro-
chemical properties using cyclic voltammetry of films drop
cast onto glassy carbon working electrodes. Figure 3 shows
cyclic voltammograms of all polymers. The IP and EA values
of the polymers are estimated from the onset oxidation and
Number-average molecular weight (Mn), weight-average molecular
weight (Mw), and polydispersity index (Mw/Mn) determined by means of
GPC with toluene as eluant on the basis of polystyrene calibration.
b
Not measured due to poor solubility in toluene.
Decomposition temperature (5% weight loss) estimated using TGA
c
under N2.
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FIGURE 2 UV-vis-NIR spectra of the polymers in 10ꢀ6 M chloroform solution (a) and in film spin coated from chloroform solution (b).
TABLE 2 Absorption Maxima of the Polymers in Solution and
polymer films exhibit typical amorphous state without any
crystalline domains. The root-mean-square (rms) roughness
of these films is in the range of 1ꢀ2.1 nm. More uniform
morphology (rms roughness of 1.065 nm) with lower defect
density was observed for polymer 1a, which is beneficial to
electron transport. To further investigate the thin film orga-
nization of the copolymers, we carried out X-ray diffraction
(XRD) measurements. None of the polymer thin films exhibit
peaks in 2y ¼ 2–30ꢂ region (1a as an example shown in Fig.
5), suggesting no crystalline structure, which is consistent
with AFM images.
in Film
opt
Polymer
Solution (nm)
Film (nm)
Eg
(eV)a
1a
1b
1c
2a
2b
3a
3b
a
351,485,619
354,484,618
357, 485, 620
369,482,736
369,486,714
448,685
350,490,630
349,485,617
354, 484, 608
369,483,747
372,492,754
451,677
1.59
1.63
1.60
1.37
1.30
1.48
1.24
492,770
490,773
Field-Effect Transistors
Estimated from the onset edge of absorption in the film.
OFET devices were fabricated in a bottom-gate, top-contact
configuration using Au as source and drain electrodes to
study the charge-transport properties of these polymers; the
transistor device parameters are summarized in Table 4. We
have previously reported n-channel OFET data acquired in
nitrogen for 1a and 2a using Al as top-contact source and
drain electrodes.8(a,b) Similar mobilities were observed in
both cases to those found in this study. The threshold vol-
tages were, however, significantly lower in the previous stud-
ies, presumably due to more facile electron injection from
larger than Egopt. This phenomenon was usually observed for
other type polymers in literatures.16
Film Morphology
Figure 4 shows atomic force microscope (AFM) height
images of the polymer films on the OTS-modified Si/SiO2
substrates spin coated from chloroform solution. All the
FIGURE 3 Cyclic voltammograms of all polymers in CH3CN/0.1 M [nBu4N]þ[PF6]ꢀ with ferrocenium/ferrocene as an internal stand-
ard, at 50 mV/s. The horizontal scale refers to an anodized Ag wire pseudo-reference electrode.
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TABLE 3 Electrochemical Properties of the Polymersa
Polymer Eox (eV) Ered (eV) IPc (eV) EAc (eV) Eg (eV)
b
b
ec
1a
1b
1c
2a
2b
3a
3b
a
þ1.03
þ1.06
þ1.12
þ0.74
þ0.51
þ0.62
þ0.58
ꢀ0.89
ꢀ0.84
ꢀ0.83
ꢀ0.90
ꢀ0.79
ꢀ0.91
ꢀ0.93
ꢀ5.83
ꢀ5.86
ꢀ5.92
ꢀ5.54
ꢀ5.31
ꢀ5.42
ꢀ5.38
ꢀ3.91
ꢀ3.96
ꢀ3.97
ꢀ3.90
ꢀ4.01
ꢀ3.89
ꢀ3.87
1.92
1.90
1.95
1.64
1.30
1.53
1.51
Thin films in CH3CN/0.1 M [nBu4N]þ[PF6]ꢀ at 50 mV/s.
b
Eox is the onset potential for oxidation vs. FeCp2þ/0; Ered is the onset
þ/0
potential for reduction vs. FeCp2
.
c
IP and EA estimated from the onset oxidation and reduction poten-
tials, respectively, assuming the absolute energy level of ferrocenium/
ferrocene to be 4.8 eV below vacuum.
FIGURE 5 X-ray diffraction pattern of 1a thin film on OTS-
modified Si/SiO2 substrate.
the lower work function Al electrodes. Comparing behavior
between the different compounds, we note the following:
exhibits ambipolar transport properties in air (Fig. 6).
Polymer 2b exhibits the largest EA (ꢀ4.01 eV) and the
smallest IP (ꢀ5.31 eV) among all the polymers, which
facilitates electron and hole injection and ambipolar trans-
port. Moreover, strong intermolecular interaction [evi-
denced by the large red shift (40 nm) of low-energy
absorption band that we observed between solution and
film] of 2b perhaps contributes to the ambipolar trans-
port. To the best of our knowledge, this is the first exam-
1. The charge-transport properties of the polymers vary con-
siderably with the variation of the N,N0-substituents of the
PDI, with the electron mobility in nitrogen varying by
nearly two orders of magnitude within the series of PDI-
DTT, 1a–c. The highest mobility is found in 1a and may
possibly be related to stronger interchain interactions in
this polymer, which also exhibits a relatively larger red
shift of the low-energy absorption band between solution
and film. The highest mobility in 1a is also attributed to
more uniform morphology with smaller rms roughness
and lower defect density. Polymers 1a–c do not function
in n-channel FET in air. For the PDI-DTP polymers, 2a
(with swallow-tail groups) exhibits only n-channel FET
behavior in nitrogen, but 2b (with propoxyethyl groups)
ple of
a PDI-based polymer to exhibit ambipolar
transport.
2. The charge-transport properties also vary with the choice
of donor. Replacing DTT with DTP in 1a to give 2a leads
to fourfold lower electron mobility and two orders of
magnitude lower on/off ratio. Increasing the number of
FIGURE 4 AFM topographic images (5 lm ꢁ 5 lm) of thin films of all polymers on OTS-modified Si/SiO2 substrates. The scale of
height images are 0 to 8 nm.
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TABLE 4 Performance of OFETs Based on the Polymers
n-Channel p-Channel
its DTP-containing counterpart (3b) exhibits p-channel
FET behavior in air, which may be related to the smaller
IP of 3b due to more electron-rich character of DTP vs.
DTT.13
Mobility (e)
(cm2/V/s)
VT
Mobility (h)
(cm2/V/s)
VT
I
on/Ioff (V)
I
on/Ioff (V)
CONCLUSIONS
1aa
1ba
1ca
2aa
1.7 ꢁ 10ꢀ2
4 ꢁ 10ꢀ3
3 ꢁ 10ꢀ4
5 ꢁ 10ꢀ3
106
13
15
14
13
17
18
27
–
We have shown that electron-transporting polymers with
good solution processability, excellent thermal stability, high
electron affinities, and in some cases high electron mobilities
can be obtained based on copolymerization of perylene dii-
mide and dithienothiophene, dithienopyrrole, or related oli-
gomeric building blocks. One of these materials is the first
example of an ambipolar PDI-based polymer. In particular,
we have investigated the effects of main chain structure and
side chain structure on the thermal, electronic, and charge
transport properties of the polymers. To summarize:
105
103
104
104
104
103
–
–
–
2bb 4 ꢁ 10ꢀ4
4 ꢁ 10ꢀ5
–
4 ꢁ 10ꢀ5
103
103
0
3aa
3bc
a
7 ꢁ 10ꢀ4
3 ꢁ 10ꢀ4
ꢀ15
In nitrogen.
b
c
In air.
In air for p-channel FET but in nitrogen for n-channel FET.
1. The absorption spectra red shift and the band gap
decreases with increasing the conjugation length of donor
block, or by replacement of DTT by DTP. Increasing the
number of DTT units, or replacing DTT with DTP, leads to
more facile oxidation (smaller IP), but affects the ease of
reduction (EA) to a lesser extent, suggesting that the
LUMOs are strongly PDI-localized. Increasing the number
of DTT units, or replacing DTT with DTP, also leads to
lower electron mobilities. However, in some cases, replac-
ing DTT with DTP leads to ambipolar transport, probably
related to the more electron-rich character of DTP vs.
DTT.
DTT units in the donor bridges between the PDIs from 1
(1a) to 3 (3a) leads to a two orders of magnitude
decrease in the electron mobility and in the on/off ratio.
Again, replacing DTT with DTP in the PDI-3DTT polymer
(3b) leads to a lower electron mobility and a lower on/
off ratio. It is possible that intrachain ET is hindered by
the more electron-rich DTP groups (in 2) and/or by the
longer bridges (in 3), while the overall dilution of elec-
tron-transporting PDI content by the N-alkyl groups of
the DTPs or by using longer bridges may hinder inter-
chain ET. Interestingly, 3a (with three DTT units) does not
exhibit p-channel FET behavior in nitrogen and in air
although it has a longer electron donating block. However,
2. The N-substituents on PDI unit exhibit little effect on the
absorption of the polymers in solution, but exhibit consid-
erable effect on the low-energy charge transfer bands and
FIGURE 6 Ambipolar OFET properties of 2b: (a) n-type output; (b) n-type transfer; (c) p-type output; (d) p-type transfer curves for a
top contact device (annealing at 140 ꢂC for 1 h, W ¼ 3 mm, L ¼ 50 lm, 100 nm film).
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Fabrication and Characterization of Field-Effect
Transistors
intermolecular interaction in film. The substituents on the
imide exhibit little impact on energy levels but significant
effect on charge transport properties of the polymers.
FET devices were fabricated with a bottom-gate top-contact
configuration. A heavily doped n-type Si wafer with a SiO2
layer of 500 nm and a capacitance of 7.5 nF/cm2 was used
as the gate. Octadecyltrichlorosilane (OTS) was used as a
self-assembled surface modifier for SiO2. A 100-nm thick (6
10 nm) semiconductor film was spin-coated on top of the
OTS-treated SiO2 from 10 mg/mL chloroform solution of the
polymers. Gold source and drain contacts (50 nm) were de-
posited on the organic layer through a shadow mask under
high vacuum. The channel length (L) and width (W) were 50
lm and 3 mm, respectively. All the measurement of electric
property was carried out in nitrogen or air using a Keithley
4200 SCS semiconductor parameter analyzer. 2b-Based de-
EXPERIMENTAL
Materials
Monomers N,N0-bis(2-decyl-tetradecyl)-1,7-dibromo-3,4:9,10-
perylene
diimide,8(a)
2,6-bis(tri-n-butylstannyl)dithieno
[3,2-b:20,30-d]thiophene,8(a) 2,6-bis(tri-n-butylstannanyl)-N-(n-
dodecyl) dithieno[3,2-b:20,30-d]pyrrole,8(b) 1,7-bis(6-bromo-
dithieno[3,2-b:20,30-d]thiophene-2-yl)-N,N0ꢀ bis(2-decyl-tetra-
decyl)-3,4:9,10-perylene diimide,8(b) and N,N0-bis(2-propox-
yethyl)-1,7-dibromo ꢀ3,4:9,10-perylene diimide (Ic),8(d) and
polymers 1a,8(a) 2a,8(b) and 3a8(b) were synthesized accord-
ing to our published procedures. 3,4,5-Tris(n-dodecyloxy)ani-
line17(a) and 2-hexyl-decylamine17(b) were synthesized
according to the literature methods. Toluene was distilled
from sodium-benzophenone under nitrogen prior to use. All
other reagents were used as received.
ꢂ
vice annealing was carried out at 140 C for 1 h in a vacuum
oven under a pressure of 0.1 Pa.
Synthesis
N,N0-Bis(2-hexyl-decyl)-1,7-dibromo-3,4:9,10-perylene
diimide (Ia)
1,7-Dibromoperylene-3,4:9,10-tetracarboxylic acid dianhy-
n
dride (1.63 g, 2.96 mmol) in 120 mL of BuOH/H2O (1:1, v/
v) was sonicated for 10 min. 2-Hexyl-decylamine (2.73 g,
11.33 mmol)ꢂ was added and the reaction mixture was
stirred at 80 C for 24 h under nitrogen. Concentrated aque-
ous HCl (13 mL) was added and the mixture was stirred at
room temperature for 30 min. The mixture was extracted
with chloroform (2 ꢁ 90 mL), washed with water (2 ꢁ 180
mL), and the extracts were dried over anhydrous MgSO4.
The solvent was removed and the residue was purified by
column chromatography over silica gel eluting with CH2Cl2/
petroleum ether (1:1) to give a red solid (1.9 g, 64%). 1H
NMR (400 MHz, CDCl3): d 9.36 (d, J ¼ 8.1 Hz, 2H), 8.81 (s,
2H), 8.59 (d, J ¼ 8.2 Hz, 2H), 4.12 (d, J ¼ 7.1 Hz, 4H), 1.98
(m, 2H), 1.5–1.1 (m, 48H), 0.85 (m, 12H). 13C NMR (100
MHz, CDCl3): d 163.0, 162.5, 138.0, 132.9, 132.6, 129.8,
129.0, 128.3, 126.8, 123.0, 122.6, 120.8, 44.8, 36.6, 32.0,
31.8, 31.6, 30.0, 29.7, 29.6, 29.3, 26.5, 22.6, 14.1. MS
(MALDI): m/z 996 (Mþ). Anal. Calcd for C56H72Br2N2O4: C,
67.46; H, 7.28; N, 2.81. Found: C, 67.53; H, 7.25; N, 2.91%.
Characterization
The 1H and 13C NMR spectra were measured on a Bruker
AVANCE 400 MHz spectrometer using tetramethylsilane
(TMS; d ¼ 0 ppm) as an internal standard. Mass spectra
were measured on a GCT-MS micromass spectrometer using
the electron impact (EI) mode or on a Bruker Daltonics
BIFLEX III MALDI-TOF Analyzer using MALDI mode. Elemen-
tal analyses were carried out using a FLASH EA1112 elemen-
tal analyzer. Solution (chloroform) and thin-film (on quartz
substrate) UV-vis-NIR absorption spectra were recorded on a
JASCO V-570 spectrophotometer. Electrochemical measure-
ments were carried out under nitrogen on a deoxygenated
solution of tetra-n-butylammonium hexafluorophosphate (0.1
M) in acetonitrile using a computer-controlled Zahner IM6e
electrochemical workstation, a glassy-carbon working elec-
trode coated with polymer films, a platinum-wire auxiliary
electrode, and an Ag wire anodized with AgCl as a pseudo-
reference electrode. Potentials were referenced to the ferro-
cenium/ferrocene (FeCp2þ/0) couple by using ferrocene as
an internal standard. Thermogravimetric analysis (TGA)
measurements were performed on Shimadzu thermogravi-
metric analyzer (model DTG-60) under a nitrogen flow at a
N,N0-Bis(3,4,5-tris(n-dodecyloxy)phenyl)-1,7-
dibromo-3,4:9,10-perylene diimide (Ib)
1,7-Dibromoperylene-3,4:9,10-tetracarboxylic acid dianhy-
dride (142 mg, 0.26 mmol) in 112 mL propionic acid was
sonicated for 10 min. 3,4,5-Tris(n-dodecyloxy)aniline (540
mg, 0.84 mmol) was added and the reaction mixture was
ꢂ
heating rate of 20 C/min. The gel permeation chromatogra-
phy (GPC) measurements were performed on a Waters 515
chromatograph connected to a Waters 2414 refractive index
detector, using toluene as eluant and polystyrene standards
as calibrants. Three Waters Styragel columns (HT2, 3, 4) con-
nected in series were used. AFM images of organic thin films
were obtained on a NanoMan VS microscope (Digital Instru-
ments) in tapping mode. The X-ray diffraction (XRD) pattern
was recorded by a Rigaku D/max-2500 diffractometer oper-
ated at 40 kV voltage and a 200 mA current with Cu Ka radi-
ation. The samples for XRD and AFM measurements were
prepared by spin-coating chloroform solution of the poly-
mers on the OTS-modified Si/SiO2 substrates.
ꢂ
stirred at 80 C for 48 h under nitrogen. The mixture cooled
down to room temperature, and then was extracted with
chloroform (2 ꢁ 100 mL); the extracts were washed with
aqueous sodium bicarbonate (2 ꢁ 150 mL) and water (2 ꢁ
150 mL), and dried over anhydrous MgSO4. The solvent was
removed and the residue was purified by column chromatog-
raphy over silica gel eluting with CH2Cl2/ petroleum ether
1
(3:1) to give a red solid (110 mg, 24%). H NMR (400 MHz,
CDCl3): d 9.45 (d, J ¼ 8.2 Hz, 2H), 8.91 (s, 2H), 8.68 (d, J ¼
8.2 Hz, 2H), 6.52 (s, 4H), 4.04 (t, J ¼ 6.2 Hz, 4H), 3.90 (t, J ¼
6.2 Hz, 8H), 1.85 (m, 12H), 1.55–1.20 (m, 108H), 0.87 (t, J ¼
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6.2 Hz, 18H). 13C NMR (100 MHz, CDCl3): d 162.6, 162.0,
153.6, 138.5, 137.9, 132.2,129.6, 129.2, 128.5, 128.1, 126.5,
123.0, 122.6, 121.2, 106.7, 73.4, 68.9, 31.9, 30.6, 29.929.8,
29.7, 29.5, 29.4, 29.3, 26.2, 26.1, 22.7, 14.1. MS (MALDI): m/
z 1807 (MHþ). Anal. Calcd for C108H160Br2N2O10: C, 71.82; H,
8.93; N, 1.55. Found: C, 71.38; H, 8.94; N, 1.64%.
and filtered through a 0.22 lm Nylon 6 filter to remove the
insoluble impurities. Removal of the solvent afforded a black
solid (640 mg, 87%). 1H NMR (400 MHz, CDCl3): d 8.7 (br,
2H), 8.3 (br, 4H), 7.6 (br, 2H), 6.5 (br, 4H), 4.0 (br, 12H), 1.9-
1.2 (br, 120H), 0.8 (br, 18H). Mw, 3.8 ꢁ 104; Mw/Mn, 1.5.
Anal. Calcd for (C116H162N2O10S3)n: C, 75.69; H, 8.87; N, 1.52.
Found: C, 74.81; H, 8.75; N, 1.41%.
Poly{[N,N0-bis(2-hexyl-decyl)-3,4:9,10-perylenediimide-1,7-
diyl]-alt-(dithieno[3,2-b:20,30-d] thiophene-2,6-diyl)} (1b)
To a 100-mL three-necked round-bottomed flask, Ia (415
mg, 0.42 mmol), 2,6-bis(tri-n-butylstannyl)dithieno[3,2-
b:20,30-d]thiophene (325 mg, 0.42 mmol), and dry toluene
(20 mL) were added. The mixture was deoxygenated with
nitrogen for 30 min. Pd(PPh3)4 (11 mg, 10 lmol) was added
Poly{[N,N0-bis(2-propoxyethyl)-3,4:9,10-
perylenediimide-1,7-diyl]-alt-(N-n-dodecyl-dithieno
[3,2-b:20,30-d]pyrrole-2,6-diyl)} (2b)
To a 100-mL three-necked round-bottomed flask, Ic (216
mg, 0.30 mmol), 2,6-bis(tri-n-butylstannyl)-N-n-dodecyl-
dithieno[3,2-b:20,30-d]pyrrole (278 mg, 0.30 mmol), and dry
toluene (10 mL) were added. The mixture was deoxygenated
with nitrogen for 30 min. Pd(PPh3)4 (40 mg, 36 lmol) was
added under nitrogen. The dark red solution was stirred at
110 ꢂC for 3 days. The black solution was cooled down to
room temperature. A solution of KF (5 g) in water (10 mL)
was added and stirred at room temperature for 2.5 h to
destroy the tin side products. The mixture was extracted
with CHCl3 (2 ꢁ 150 mL), washed with water (2 ꢁ 300 mL),
and the extracts were dried over anhydrous MgSO4. The so-
lution was concentrated to 5 mL, and then dropped into 200
mL of methanol. The black precipitate was filtered, and
washed with methanol. The black solid was Soxhlet extracted
with acetone for 2 days. Finally, the polymer was purified by
size exclusion column chromatography over Bio-Rad Bio-
Beads S-X1 eluting with CHCl3. Polymer 2b was dissolved in
chloroform and filtered through a 0.22 lm Nylon 6 filter to
remove the insoluble impurities. Removal of the solvent
afforded a black solid (240 mg, 89%). 1H NMR (400 MHz,
CDCl3): d 8.7 (br, 2H), 8.3 (br, 4H), 7.4 (br, 2H), 4.5 (br, 6H),
3.8 (br, 4H), 3.5 (br, 4H), 1.9 (br, 2H), 1.7–1.2 (br, 22H), 0.8
(br, 9H). Mw, 8.2 ꢁ 104; Mw/Mn, 1.8. Anal. Calcd for
ꢂ
under nitrogen. The dark red solution was stirred at 110 C
for 2 days. The resulting black sticky solution was cooled
down to room temperature. A solution of KF (5 g) in water
(10 mL) was added and stirred at room temperature for 2 h
to destroy the tin side products. The mixture was extracted
with CH2Cl2 (2 ꢁ 150 mL), washed with water (2 ꢁ 300
mL), and the extracts were dried over anhydrous MgSO4.
The solution was concentrated to 15 mL, then dropped into
300 mL of methanol. The black precipitate was filtered, and
washed with methanol. The black solid was redissolved in
60 mL of CH2Cl2, then dropped into 500 mL of acetone. The
black precipitate was filtered, and Soxhlet extracted with ac-
etone for 2 days. Finally, the polymer was purified by size
exclusion column chromatography over Bio-Rad Bio-Beads S-
X1 eluting with CHCl3. Polymer 1b was dissolved in chloro-
form and filtered through a 0.22 lm Nylon 6 filter to remove
the insoluble impurities. Removal of the solvent afforded a
1
black solid (387 mg, 88%). H NMR (400 MHz, CDCl3): d 8.7
(br, 2H), 8.3 (br, 4H), 7.6 (br, 2H), 4.1 (br, 4H), 2.0 (br, 2H),
1.2 (br, 48H), 0.8 (br, 12H). Anal. Calcd for (C64H74N2O4S3)n:
C, 74.52; H, 7.23; N, 2.72. Found: C, 73.59; H, 7.16; N, 2.63%.
C54H55N3O6S2: C, 71.57; H, 6.12; N, 4.64. Found: C, 70.56; H,
Poly{[N,N0-bis(3,4,5-tris(n-dodecyloxy)phenyl)-
3,4:9,10-perylene diimide-1,7-diyl]-alt- (dithieno
[3,2-b:20,30-d]thiophene-2,6-diyl)} (1c)
6.05; N, 4.48%.
Poly{[1,7-bis-2-dithieno[3,2-b:20,30-d]thiophene-N,N0-bis
(2-decyl-tetradecyl)-3,4:9,10-perylene ꢀdiimide-6,60-diyl]-
alt-(N-n-dodecyl-dithieno[3,2-b:20,30-d]pyrrole-2,6-diyl)} (3b)
To a 100-mL three-necked round bottom flask, 1,7-bis
(6-bromo- dithieno[3,2-b:20,30-d]thiophene-2-yl)-N,N0-bis(2-
decyl-tetradecyl)-3,4:9,10-perylene diimide (403 mg, 0.25
mmol), 2,6-bis(tri-n-butylstannyl)-N-n-dodecyl-dithieno[3,2-
b:20,30-d]pyrrole (232 mg, 0.25 mmol), and dry toluene (10
mL) were added. The mixture was deoxygenated with nitro-
gen for 30 min. Pd(PPh3)4 (22 mg, 20 lmol) was added
To a 100-mL three-necked round-bottomed flask, Ib (722
mg, 0.4 mmol), 2,6-bis(tri-n-butylstannyl)dithieno[3,2-b:20,30-
d]thiophene (310 mg, 0.4 mmol), and dry toluene (20 mL)
were added. The mixture was deoxygenated with nitrogen
for 30 min. Pd(PPh3)4 (47 mg, 40 lmol) was added under
nitrogen. The dark red solution was stirred at 110 ꢂC for 2
days. The black sticky solution was cooled down to room
temperature. A solution of KF (5 g) in water (10 mL) was
added and stirred at room temperature for 2 h to destroy
the tin side products. The mixture was extracted with CH2Cl2
(2 ꢁ 150 mL), washed with water (2 ꢁ 300 mL), and the
extracts were dried over anhydrous MgSO4. The solution was
concentrated to 15 mL, then dropped into 300 mL of metha-
nol. The black precipitate was filtered and washed with
methanol. The black solid was redissolved in 60 mL of
CH2Cl2, and then dropped into 500 mL of acetone. The black
precipitate was filtered, and Soxhlet extracted with acetone
for 2 days. Finally, the polymer was purified by size exclu-
sion column chromatography over Bio-Rad Bio-Beads S-X1
eluting with THF. Polymer 1c was dissolved in chloroform
ꢂ
under nitrogen. The dark red solution was stirred at 110 C
for 3 days. A solution of KF (5 g) in water (10 mL) was
added and stirred at room temperature for 2.5 h to destroy
the tin side products. The mixture was extracted with CHCl3
(2 ꢁ 150 mL), washed with water (2 ꢁ 300 mL), and the
extracts were dried over anhydrous MgSO4. The solution was
concentrated to 5 mL, and then dropped into 200 mL of
methanol. The black precipitate was filtered and washed
with methanol. Finally, the polymer was purified by size
exclusion column chromatography over Bio-Rad Bio-Beads S-
X1 eluting with CHCl3. Polymer 3b was dissolved in
8
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5 H. Usta, A. Facchetti, T. Marks, J. Am. Chem. Soc. 2008, 130,
8580–8581.
chloroform and filtered through a 0.22 lm Nylon 6 filter to
remove the insoluble impurities. Removal of the solvent
afforded a black solid (406 mg, 91%). 1H NMR (400 MHz,
CDCl3): d (ppm) 8.8 (br, 2H), 8.4 (br, 4H), 7.4 (br, 2H), 7.1 (br,
4H), 4.4-4.1 (br, 6H), 2.0 (br, 4H), 1.3 (br, 98H), 0.8 (br, 15H).
Mw, 1.6 ꢁ 104; Mw/Mn, 1.7. Anal. Calcd for C108H135N3O4S8: C,
72.23; H, 7.58; N, 2.34. Found: C, 71.20; H, 7.51; N, 2.17%.
6
(a) X. W. Zhan, A. Facchetti, S. Barlow, T. J. Marks, M. A.
Ratner, M. R. Wasielewski, S. R. Marder, Adv. Mater. 2011, 23,
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7
(a) R. J. Chesterfield, J. C. McKeen, C. R. Newman, P. C.
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Ewbank, D. A. da Silva Filho, J.-L. Bredas, L. L. Miller, K. R.
Mann, C. D. Frisbie, J. Phys. Chem. B 2004, 108, 19281–19292; (b)
S. Tatemichi, M. Ichikawa, T. Koyama, Y. Taniguchi, Appl. Phys.
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ACKNOWLEDGMENTS
This material is based upon work supported in part by the
NSFC (Grants 21025418, 50873107, 21021091), 973 Project
(Grant 2011CB808401), the Chinese Academy of Sciences, and
Solvay S. A.
8
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