"conformation Locked" Strong Electron-Deficient Poly(p -Phenylene Vinylene) Derivatives for Ambient-Stable n-Type Field-Effect Transistors: Synthesis, Properties, and Effects of Fluorine Substitution Position

Article abstract of DOI:10.1021/ja412533d

The charge carrier mobility of p-type and ambipolar polymer field-effect transistors (FETs) has been improved substantially. Nonetheless, high-mobility n-type polymers are rare, and few can be operated under ambient conditions. This situation is mainly ca

Full text of DOI:10.1021/ja412533d

Article
pubs.acs.org/JACS
“Conformation Locked” Strong Electron-Deficient Poly(p‑Phenylene
Vinylene) Derivatives for Ambient-Stable n‑Type Field-Effect
Transistors: Synthesis, Properties, and Effects of Fluorine
Substitution Position
Ting Lei,† Xin Xia,‡ Jie-Yu Wang,†,* Chen-Jiang Liu,‡,* and Jian Pei†,*
†Beijing National Laboratory for Molecular Sciences, the Key Laboratory of Bioorganic Chemistry and Molecular Engineering of
Ministry of Education, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, People’s Republic of
China
‡Physics and Chemistry Detecting Center, the Key Laboratory of Oil & Gas Fine Chemicals of Ministry of Education, School of
Chemistry and Chemical Engineering, Xinjiang University, Urumqi 830046, People’s Republic of China
S
* Supporting Information
ABSTRACT: The charge carrier mobility of p-type and
ambipolar polymer field-effect transistors (FETs) has been
improved substantially. Nonetheless, high-mobility n-type
polymers are rare, and few can be operated under ambient
conditions. This situation is mainly caused by the scarcity of
strong electron-deficient building blocks. Herein, we present
two novel electron-deficient building blocks, FBDOPV-1 and
FBDOPV-2, with low LUMO levels down to −4.38 eV. On
the basis of both building blocks, we develop two poly(p-
phenylene vinylene) derivatives (PPVs), FBDPPV-1 and
FBDPPV-2, for high-performance n-type polymer FETs.
The introduction of the fluorine atoms effectively lowers the
LUMO levels of both polymers, leading to LUMO levels as low as −4.30 eV. Fluorination endows both polymers with not only
lower LUMO levels, but also more ordered thin-film packing, smaller π−π stacking distance, stronger interchain interaction and
locked conformation of polymer backbones. All these factors provide FBDPPV-1 with high electron mobilities up to 1.70 cm2
V−1 s−1 and good stability under ambient conditions. Furthermore, when polymers have different fluorination positions, their
backbone conformations in solid state differ, eventually leading to different device performance.
electronics, because both n-type and p-type semiconductors
are necessary to achieve low power complementary circuits.23
To date, the development of strong electron-deficient
building blocks remains essential to advancing n-type polymer
semiconductors.18,19 Introducing electron-withdrawing groups
can effectively lower the lowest unoccupied molecular orbital
(LUMO) level of a known building block.24,25 For example,
fluorination of polymer backbones can improve the perform-
ance of organic photovoltaics26,27 and increase the electron
mobility of ambipolar polymer FETs.28,29 Obviously, fluorina-
tion can modulate the energy-level of conjugated polymers;
nonetheless, it must have other influences on polymer
properties, which are important yet seldom investigated.
Charge transport in conjugated polymer films generally
contains intrachain and interchain transport. The intrachain
mobility of conjugated polymers can be very high.30 Reducing
torsional angles or using shape-persistent backbones will
enhance intrachain transport through increasing effective
INTRODUCTION
■
Conjugated polymers are promising active layers for low-cost
flexible electronics because their optoelectronic properties can
be tuned, and they are solution processable, mechanically
flexible, and compatible with heat-sensitive substrates.1 The
development of novel building blocks and fabrication processes
have led to significant progress of polymer semiconductors.2−4
For instance, polymer field-effect transistors (FETs) have been
significantly developed due to the design and application of
electron-deficient aromatics, such as benzothiadiazole (BT),5,6
naphthalene diimide (NDI),7,8 benzobisthiadiazole (BBT),9,10
diketopyrrolopyrrole (DPP),3,11−13 and isoindigo (II)14−17
(Figure 1). High hole mobilities over 10 cm2 V−1 s−1 have
been achieved for polymer FETs,12,13 which are comparable
with the performance of vacuum-deposited organic thin-film
transistors and many organic single-crystal transistors.18
Compared to many high-mobility p-type polymers, high-
mobility n-type polymers are rare, and few can be operated
under ambient conditions.8,19−22 Developing ambient-stable n-
type semiconductors becomes a critical issue in organic
Received: December 10, 2013
Published: January 15, 2014
© 2014 American Chemical Society
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still undergoes conformational disorder in solid state. More-
over, although this polymer exhibited outstanding stability in n-
type polymer FETs, its device performance still deteriorates
under ambient conditions.
Herein, we attempt to “lock” the remaining one-third of the
double bonds in BDPPV by introducing fluorine atoms to form
more intramolecular hydrogen bonds (Figure 2). We first
synthesized two new building blocks, FBDOPV-1 and
FBDOPV-2, with fluorine atoms at different positions of
BDOPV. Both of them have perhaps the lowest LUMO levels
(down to −4.38 eV) in polymer building blocks reported to
date. Then they were used to prepare two new PPV derivatives,
FBDPPV-1 and FBDPPV-2 (Figure 2).18 Fluorine atoms can
lower the LUMO levels and fully “lock” the conformations of
polymer backbones through intramolecular hydrogen bonds.
High-performance n-type FETs based on these two polymers
were fabricated. To our delight, FBDPPV-1 exhibits electron
mobilities up to 1.70 cm2 V−1 s−1 under ambient conditions,
which is among the highest in n-type conjugated polymers and
is also a new record for ambient-stable n-type polymer
FETs.8,18,19 Both polymers have improved stability under
ambient conditions due to their low-lying LUMO levels. In
addition, when the fluorine atoms are substituted in different
positions of the polymer backbone, different conformations are
created, which eventually leads to different device performance.
Figure 1. Chemical structures and HOMO/LUMO levels of several
electron-deficient building blocks used for high-performance polymer
FETs.4
conjugation length.30 For interchain transport, shape-persistent
polymer backbones and well-ordered backbone conformations
are anticipated because they could provide better π−π
interactions and ordered polymer packing.31 Recently,
benzodifurandione-based oligo(p-phenylene vinylene)
(BDOPV) was developed for ambipolar and n-type polymer
FETs (Figure 1).32−34 BDOPV is an electron-deficient building
block, which can be regarded as a derivative of oligo(p-
phenylene vinylene) (OPV). It has four electron-withdrawing
carbonyl groups and a low LUMO level of −4.24 eV,
significantly lower than those of many electron-deficient
building blocks (Figure 1). In addition, these carbonyl groups
form four intramolecular hydrogen bonds with the neighboring
phenyl protons, making BDOPV planar and shape-persistent.
Using BDOPV as building block, we prepared benzodifur-
andione-based poly(p-phenylene vinylene) (BDPPV) (Figure
2).32 This polymer has high electron mobilities up to 1.1 cm2
RESULTS AND DISCUSSION
■
Design Strategy and Synthesis. Construction of donor−
acceptor polymers can achieve high carrier mobilities.1,4
Nonetheless, we did not use this strategy in the design of a
“pure” n-type transporting system, because this strategy usually
increases the highest occupied molecular orbital (HOMO)
levels of conjugated polymers, resulting in hole injection, low
on/off ratio, or ambipolar transport.33,34 Moreover, electron-
rich donors also increase the LUMO levels of conjugated
polymers, thus making the electron transport more susceptible
to oxygen and moisture.35 Alternatively, a double bond was
used to link the BDOPV units due to its weak electron-
donating property. Furthermore, we and other groups have
demonstrated that carrier mobilities of conjugated polymers
could be significantly increased by using farther branched alkyl
chains.11,15,36,37 Thus, long and farther branched 4-octadecyl-
docosyl groups were used as polymer side chains to guarantee
both better interchain interactions and good solubility. To
understand how fluorination influences the conjugated
polymers, we prepared two similar polymers with different
fluorinated positions (Figure 2).
Scheme 1 illustrates the synthetic route to FBDPPV-1 and
FBDPPV-2. The synthesis of fluorinated BDOPV started from
the construction of fluorinated 6-bromoisatin. 6-Bromo-7-
fluoroisatin (1) was synthesized according to our previous
report.29 6-Bromo-5-fluoroisatin (7) was synthesized from
commercially available 3-bromo-4-fluoroaniline by the con-
densation reaction of chloral hydrate and hydroxylamine
hydrochloride, followed by catalyzed cyclization using sulfuric
acid. Both fluorinated isatins (1 and 7) were then alkylated with
19-(3-iodopropyl)heptatriacontane (2) in the presence of
K2CO3, and both compounds 3 and 8 were obtained in good
yields. FBDOPV-1 or FBDOPV-2 were readily obtained with
67% or 78% yield by using a simple acidic condensation
condition between 3 or 8 and 2,2′-(2,5-dihydroxy-1,4-
phenylene)diacetic acid (9), respectively.33 Microwave-assisted
Stille coupling polymerizations using (E)-1,2-bis-
Figure 2. Design strategy of fully “conformation locked” PPV-based
conjugated polymers, FBDPPV-1 and FBDPPV-2.
V−1 s−1, because it overcomes common defects in poly(p-
phenylene vinylene) derivatives (PPVs), such as conforma-
tional disorder (freely rotating double-bonds), weak interchain
interaction, and high LUMO level.32 Nonetheless, only two-
third of the double bonds in this polymer are “locked” by
intramolecular hydrogen bonds, thus the polymer backbone
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Scheme 1. Synthetic Route to Fluorinated BDOPV Derivatives and Fluorinated BDPPV Polymers
Figure 3. (a) Cyclic voltammograms of BDOPV (with bromine), FBDOPV-1 and FBDOPV-2 in 1,2-dichlorobenzene (DCB) solution (5 mg/mL).
(b) Normalized absorption spectra of three polymers in CHCl3 (10−5 M). (c) Normalized absorption spectra of FBDPPV-1 in CHCl3 (10−5 M),
thin film and annealed film (180 °C for 30 min). (d) Cyclic voltammograms of three polymers in drop-casted film prepared using their chloroform
solutions (5 mg/mL). (e) Molecular frontier orbitals of the FBDPPV-1 trimer (B3LYP/6-311G(d,p)).
(tributylstannyl)ethene gave polymers FBDPPV-1 and
FBDPPV-2 in 96% and 83% yield, respectively. The molecular
weights of both polymers were evaluated by high-temperature
(GPC) at 140 °C using 1,2,4-tricholorobenzene (TCB) as
eluent. Both polymers displayed comparable molecular weights
(FBDPPV-1: Mw = 128.9 kDa, Mn = 66.3 kDa, PDI = 1.94;
FBDPPV-2: Mw = 164.7 kDa, Mn = 53.8 kDa, PDI = 3.06)
(Figure S1 in the Supporting Information, SI) and showed
excellent thermal stability with decomposition temperatures
over 370 °C (Figure S2 in the SI).
Photophysical and Electrochemical Properties. The
aborption sprectra of FBDOPV-1 and FBDOPV-2 are
smimilar to that of BDOPV (with bromine on the same
position as FBDOPV) due to their identical conjugated
backbones (Figure S3 in the SI). After introducing fluorine
atoms, both the HOMO and LUMO energy levels of
FBDOPV-1 and FBDOPV-2 are lowered. The LUMO energy
levels are lowered by 0.14 and 0.12 eV for FBDOPV-1 and
FBDOPV-2, respectively (Table S1 in the SI). The LUMO
level of FBDOPV-1 reaches −4.38 eV, suggesting that
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Table 1. Summary of Optical and Electrochemical Properties, OFET Device Performance and GIXD Results of Three Polymers
e
d (Å)
a
b
c
c
d
μ (cm2 V−1 s−1
)
VT (V)
log (Ion/Ioff)
sol
film
compounds
λmax (nm)
λmax (nm)
Eg (eV)
EHOMO (eV)
ELUMO (eV)
L
π
BDPPV
799, 728
786, 710
803, 724
784, 710
808, 743
1.42
1.46
1.39
−6.12
−6.19
−6.22
−4.10
−4.26
−4.30
1.10 (0.84)
1.70 (1.39)
+5
+18
+1
5−6
5−6
4−5
32.3
32.9
32.7
3.45
3.42
3.42
FBDPPV-1
FBDPPV-2
800, 740
0.81 (0.62)
c
a
b
10−5 M in chloroform. Estimated from the onset of the absorption spectra of thin film. Cyclic voltammetry determined with Fc/Fc+ (EHOMO
−4.80 eV) as external reference. Maximum values of the electron mobilities. Electron mobilities are measured under ambient conditions (RH = 50−
60%). The average values are in parentheses. Lamellar (L) and π−π stacking (π) distances determined by GIXD experiments.
=
d
e
Figure 4. 2D-GIXD patterns and AFM height images of (a, d) BDPPV, (b, e) FBDPPV-1, and (c, f) FBDPPV-2 films. Films were prepared by spin-
coating their DCB solutions (3 mg/mL) and annealed at 180 °C for 30 min.
FBDOPV-1 is one of the most electron-deficient building
blocks for conjugated polymers.4,38 Note that all three
monomers display two reversible reductive peaks in solution
(Figure 3a), indicating their good stability in the anionic state.
All these polymers show similar absorption spectra, and all
have two absoprtion bands (Band I: 600−900 nm; Band II:
400−600 nm) and low bandgaps around 1.4 eV (Figure 3 and
Table 1). All polymers have structured vabrational absorption
peaks in the Band I region, which agrees well with their shape-
persistent conjugated backbones. Compared with BDPPV,
FBDPPV-1 exihbits a blue-shifted absorption spectrum,
whereas FBDPPV-2 exihbits a slightly red-shift. In addtion,
three polymers show different oscillator strength of the
vabrational absorption peaks. The main absorption peak of
FBDPPV-1 in film only shows very little red-shift compared to
that in solution, and an obvious increase of the relative intensity
of its 0−0 vibrational peak is observed (Figure 3c). Annealing
the film results in a further increase of the relative intensity of
0−0 peak, indicating that the polymer backbone becomes more
planar in film and annealing is helpful for further adjustment.
For conjugated polymers, intermolecular stacking and con-
formational change may significantly shift the absorption
spectra.39 However, no significant change was observed from
solution to thin film for FBDPPV-1, suggesting that the
polymer probably formed some preaggregates in solution due
to strong interchain interactions.40,41 Compared with
FBDPPV-1, FBDPPV-2 shows a little more red-shifted
absorption from solution to film (Figure S4 in the SI),
suggesting that both polymers might take different molecular
conformations and supramolecular organizations in solid state,
although they have very similar conjugated backbones.39
Electrochemical properties of three polymers were explored
by cyclic voltammetry (CV) measurement (Figure 3d). After
introducing fluorine atoms, the reductive currents of both
fluorinated polymers increase obviously and the reductive
doping processes appear to be more reversible than those of
BDPPV. Both the HOMO and LUMO energy levels of
FBDPPV-1 and FBDPPV-2 are lowered, but clearly the
LUMO energy levels are more easily affected (Table 1). The
LUMO levels of FBDPPV-1 and FBDPPV-2 reach −4.26 and
−4.30 eV, 0.16 and 0.20 eV lower than that of BDPPV. To our
knowledge, these polymers are the most electron-deficient
conjugated polymers reported to date.8,19,22,42,43 Computa-
tional results reveal that both fluorinated polymers exhibit
almost planar conjugated backbones and their HOMOs and
LUMOs are well delocalized along polymer backbones (Figure
3e). This contrasts with many donor−acceptor polymers, in
which the LUMOs are mostly localized on the electron-
deficient cores of polymer backbones.16,34
Thin Film Microstructural Characterization. The
molecular packings and surface morphologies of three polymer
films were invesitgated by grazing incident X-ray diffraction
(GIXD) and tapping-mode atomic force microscopy (AFM)
(Figure 4). Three polymers display strong out-of-plane
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diffractions (h00), indicating that good edge-on lamellar
packings are formed in film. Fluorinated polymers show five
out-of-plane diffraction peaks, whereas BDPPV only shows four
out-of-plane peaks. However, three polymers exihbit similar
lamellar distances around 32 Å due to their smiliar backbones
and identical side chains. (010) Peaks attributed to π−π
stacking were also observed. Clearly, both fluorinated polymers
exhibt a stronger (010) peak with a shorter π−π stacking
distance of 3.42 Å, slightly shorter than that of BDPPV (3.45
Å). These results suggest that after introducing fluorine atoms,
FBDPPV-1 and FBDPPV-2 exhibit more ordered lamellar
packing and stronger interchain interactions in solid state. This
is also supported by the AFM observation that both fluorinated
polymers display fiber-like intercalating networks with
obviously crystallized zones. Root-mean-square (RMS) analysis
of the height data shows that the films of fluorinated polymers
display larger roughness, presumably due to their stronger
crystallinity. Therefore, the introduction of fluorine atoms not
only modulates the energy levels of polymers, but also
influences the interchain interactions and polymer packing in
solid state.
semiconducting layer was deposited by spin-coating a polymer
solution (3 mg/mL in DCB) on Au (source-drain)/SiO2/Si
substrate. After thermal annealing, a CYTOP solution was spin-
coated on the top of the semiconducting layer and cross-linked
under 100 °C for 1 h, providing the dielectric layer (500 nm
thick). Then, an aluminum layer was thermally evaporated as
the gate electrode. All devices were fabricated in glovebox and
tested under ambient conditions (RH = 50−60%). Both
fluorinated polymers show typical n-type transport character-
istics under ambient conditions (Figure 5b,d). The maximum
mobility of the FBDPPV-1 devices was determined to be as
high as 1.70 cm2 V−1 s−1, which is among the highest in n-type
conjugated polymers and is also a new record for n-type
polymer FETs operated under ambient conditions.8,19 Note
that FBDPPV-1 shows typical transfer and output character-
istics with negligible hysteresis, which is seldom observed for n-
type organic materials, largely attributed to its significantly
lowered LUMO level. Besides, no contact resistance was
observed in output curves, suggesting a good contact between
the polymer and gold electrode. However, FBDPPV-2 only
gave the highest electron mobility of 0.81 cm2 V−1 s−1 and an
average mobility of 0.62 cm2 V−1 s−1, unexpectedly lower than
that of nonfluorinated BDPPV (highest: 1.10 cm2 V−1 s−1;
average: 0.84 cm2 V−1 s−1).
Time-dependent decays of three polymer devices were tested
by storing the devices under ambient conditions (RH = 50−
60%). All polymers show good stability with a slow roll-off of
electron mobility (Figure 5e). Fluorinated polymers show
obviously better stability than nonfluorinated BDPPV. After 30
days, the mobility of FBDPPV-1 device decreased from 1.61 to
1.13 cm2 V−1 s−1, whereas that of BDPPV decreased from 1.10
to 0.31 cm2 V−1 s−1. The decay of the electron mobilities may
be caused by the further diffusion of oxygen or moisture into
the semiconducting layer.35 Although these devices are not
long-term stable under ambient conditions, these results are
outstanding among n-type conjugated polymers, because few
reported n-type polymers can be operated under ambient
conditions.8,19−22
Field-Effect Transistor Fabrication and Measure-
ments. Top-gate/bottom-contact (TG/BC) device configu-
ration was used to evaluate the carrier transport of both
fluorinated polymers (Figure 5a). This device configuration is
preferred for many n-type organic materials because of its
better injection characteristics and encapsulation effect.8 The
Influence of Backbone Conformation on Carrier
Mobility. Both fluorinated polymers have considerably differ-
ent device performance despite their similar physical and
electrochemical properties, including molecular weight, thin-
film packing, and morphology. We propose that this difference
originates from their different polymer backbone conformations
in solid state. To give a better understanding, a model
compound (E)-1,2-bis(2-fluorophenyl)ethane was used to
investigate the double bond conformations of the fluorinated
polymers. Figure 6a displays three possible conformations of
the model compound. After introducing fluorine atoms,
intramolecular hydrogen bonds are formed between fluorine
and hydrogen atoms, thus locking the molecular conformation.
The five-membered-ring hydrogen bonding is preferred,
providing obviously lower energy than the six-membered-ring
hydrogen bonding. This computational analysis is supported by
single crystal structures of several fluorinated OPV deriva-
tives,44 in which all of the fluorine atoms formed five-
membered-ring hydrogen bonds with neighboring phenyl
protons (Figure 6b). These results indicate that both
FBDPPV-1 and FBDPPV-2 may have “locked” conformations
and intramolecular five-membered-ring hydrogen bonds are
formed in solid state. Clearly, due to the different substitution
position of fluorine, the backbone conformations of both
polymers are different. Calculations on the oligomers of
Figure 5. (a) Top-gate/bottom-contact device configuration used in
this study. (b) Transfer and (c) output characteristics of a FBDPPV-1
device measured under ambient conditions. (d) Transfer characteristic
of a FBDPPV-2 device. (e) Time-dependent decays of the device
performance of three polymers under ambient conditions. FET devices
(L = 5 μm, W = 100 μm,) were fabricated with CYTOP layers around
500 nm thick (capacitance Ci = 3.7 nF cm−2).
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Figure 6. (a) Energy diagram of different planar conformations of model compound (E)-1,2-bis(2-fluorophenyl)ethane (calculated at B3LYP/6-
311+G(d,p) level). (b) Single crystal structures of two fluorinated OPV derivatives. Both show five-membered-ring intramolecular hydrogen bonds.
(c) Proposed intramolecular hydrogen bonds and backbone conformations for FBDPPV-1 and FBDPPV-2.
FBDPPV-1 also show that the five-membered-ring hydrogen-
bonding conformation is more stable than other conformations
(Figure S7 in the SI).
CONCLUSIONS
■
In conclusion, we have developed two novel strong electron-
deficient building blocks, FBDOPV-1 and FBDOPV-2. Both
building blocks have extremely low LUMO levels down to
−4.38 eV. On the basis of them, two PPV derivatives,
FBDPPV-1 and FBDPPV-2, are developed for ambient-stable
n-type polymer FETs. Both polymers exhibit improved device
stability under ambient conditions due to their low-lying
LUMO levels. FBDPPV-1 has increased electron mobility up
to 1.70 cm2 V−1 s−1 under ambient conditions, which is among
the highest in n-type conjugated polymers, whereas FBDPPV-2
has decreased electron mobility. Our work demonstrates that
fluorination is more than lowering the energy levels of
conjugated polymers, it can also influence backbone con-
formations (hence interchain interactions and film micro-
structures), which is critical to the device performance. Given
the extensive application of fluorination in conjugated
polymers, the systematic comparison and conformational
consideration presented in this work could provide a new
angle to investigate the structure−property relationships of
conjugated polymers.
Using a computational method, Beljonne and co-workers
demonstrated that interchain charge transport correlates with
the supramolecular organization of conjugated polymers.45 For
example, even under the same π−π stacking distance, different
polymer packing conformations can lead to greatly different
interchain carrier transport. This is mainly caused by the
different charge transfer integrals between polymer chains.46
Furthermore, increasing experimental results suggest that
polymer backbone conformations indeed exert their influences
on carrier transport through adopting various interchain
molecular packings.47,48 Figure 6c shows the proposed
intramolecular hydrogen bonds in FBDPPV-1 and FBDPPV-
2 and their polymer backbone conformations in film. The
purple arrows indicate the included angles between the alkyl
chain extending directions and the polymer backbone
extending directions. Clearly, the double bond orientations
are different for both polymers, and the included angle of
FBDPPV-1 is close to 90o, obviously larger than that of
FBDPPV-2. This analysis agrees with the absorption spectra
result that both polymers might have different molecular
conformations and supramolecular organization in solid state.
Because intermolecular packing and carrier mobility are
sensitive to molecular conformations and the orientation of
side chains,46,49,50 the different backbone conformations of
FBDPPV-1 and FBDPPV-2 might lead to different interchain
organization and thereby influence interchain carrier transport.
Similarly, due to the ineffective interchain charge transport,
FBDPPV-2 exhibits lower electron mobility than BDPPV, even
though it has locked conformations, lower LUMO level and
stronger crystallinity. However, further investigations are
needed to better understand the myriad factors influencing
the electron transport of these polymers, but are beyond the
scope of this manuscript.
ASSOCIATED CONTENT
■
S
* Supporting Information
OTFT fabrication details; GPC, TGA, and DSC traces; UV−vis
spectra; monomer and polymer synthesis and characterization;
and 1H and 13C NMR spectra. This material is available free of
charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
jianpei@pku.edu.cn; pxylcj@126.com; jieyuwang@pku.edu.cn
Notes
The authors declare no competing financial interest.
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(31) Noriega, R.; Rivnay, J.; Vandewal, K.; Koch, F. P. V.; Stingelin,
N.; Smith, P.; Toney, M. F.; Salleo, A. Nat. Mater. 2013, 12, 1038−
1044.
ACKNOWLEDGMENTS
■
This work was supported by the Major State Basic Research
Development Program (2013CB933501) from the Ministry of
Science and Technology, Urumqi Science and Technology
Project (G121120005), and National Natural Science Founda-
tion of China. The authors thank beamline BL14B1 (Shanghai
Synchrotron Radiation Facility) for providing the beam time.
(32) Lei, T.; Dou, J.-H.; Cao, X.-Y.; Wang, J.-Y.; Pei, J. J. Am. Chem.
Soc. 2013, 135, 12168−12171.
(33) Yan, Z.; Sun, B.; Li, Y. Chem. Commun. 2013, 49, 3790−3792.
(34) Lei, T.; Dou, J. H.; Cao, X. Y.; Wang, J. Y.; Pei, J. Adv. Mater.
2013, 25, 6589−6593.
(35) Di Pietro, R.; Fazzi, D.; Kehoe, T. B.; Sirringhaus, H. J. Am.
Chem. Soc. 2012, 134, 14877−14889.
REFERENCES
■
(36) Lei, T.; Dou, J.-H.; Pei, J. Adv. Mater. 2012, 24, 6457−6461.
(37) Zhang, F.; Hu, Y.; Schuettfort, T.; Di, C.-A.; Gao, X.; McNeill,
C. R.; Thomsen, L.; Mannsfeld, S. C. B.; Yuan, W.; Sirringhaus, H.;
Zhu, D. J. Am. Chem. Soc. 2013, 135, 2338−2349.
(38) Wen, Y.; Liu, Y.; Guo, Y.; Yu, G.; Hu, W. Chem. Rev. 2011, 111,
3358−3406.
(1) Heeger, A. J. Chem. Soc. Rev. 2010, 39, 2354−2371.
(2) Mei, J.; Diao, Y.; Appleton, A. L.; Fang, L.; Bao, Z. J. Am. Chem.
Soc. 2013, 135, 6724−6746.
(3) Nielsen, C. B.; Turbiez, M.; McCulloch, I. Adv. Mater. 2013, 25,
1859−1880.
(4) Yuen, J. D.; Wudl, F. Energy Environ. Sci. 2013, 6, 392−406.
(5) Tsao, H. N.; Cho, D. M.; Park, I.; Hansen, M. R.; Mavrinskiy, A.;
(39) Kim, J.; Swager, T. M. Nature 2001, 411, 1030−1034.
(40) Steyrleuthner, R.; Schubert, M.; Howard, I.; Klaumunzer, B.;
̈
Yoon, D. Y.; Graf, R.; Pisula, W.; Spiess, H. W.; Mullen, K. J. Am.
Chem. Soc. 2011, 133, 2605−2612.
̈
Schilling, K.; Chen, Z.; Saalfrank, P.; Laquai, F.; Facchetti, A.; Neher,
D. J. Am. Chem. Soc. 2012, 134, 18303−18317.
(6) Tseng, H.-R.; Ying, L.; Hsu, B. B. Y.; Perez, L. A.; Takacs, C. J.;
Bazan, G. C.; Heeger, A. J. Nano Lett. 2012, 12, 6353−6357.
(7) Zhan, X.; Facchetti, A.; Barlow, S.; Marks, T. J.; Ratner, M. A.;
Wasielewski, M. R.; Marder, S. R. Adv. Mater. 2011, 23, 268−284.
(8) Yan, H.; Chen, Z.; Zheng, Y.; Newman, C.; Quinn, J. R.; Dotz, F.;
Kastler, M.; Facchetti, A. Nature 2009, 457, 679−686.
(9) Fan, J.; Yuen, J. D.; Cui, W.; Seifter, J.; Mohebbi, A. R.; Wang,
M.; Zhou, H.; Heeger, A.; Wudl, F. Adv. Mater. 2012, 24, 6164−6168.
(10) Yuen, J. D.; Fan, J.; Seifter, J.; Lim, B.; Hufschmid, R.; Heeger,
A. J.; Wudl, F. J. Am. Chem. Soc. 2011, 133, 20799−20807.
(11) Lee, J.; Han, A. R.; Yu, H.; Shin, T. J.; Yang, C.; Oh, J. H. J. Am.
Chem. Soc. 2013, 135, 9540−9547.
(41) Zhou, N.; Guo, X.; Ortiz, R. P.; Li, S.; Zhang, S.; Chang, R. P.
H.; Facchetti, A.; Marks, T. J. Adv. Mater. 2012, 24, 2242−2248.
(42) Usta, H.; Newman, C.; Chen, Z.; Facchetti, A. Adv. Mater. 2012,
24, 3678−3684.
(43) Chen, Z.; Zheng, Y.; Yan, H.; Facchetti, A. J. Am. Chem. Soc.
2009, 131, 8−9.
(44) Renak, M. L.; Bartholomew, G. P.; Wang, S.; Ricatto, P. J.;
Lachicotte, R. J.; Bazan, G. C. J. Am. Chem. Soc. 1999, 121, 7787−
7799.
(45) Niedzialek, D.; Lemaur, V.; Dudenko, D.; Shu, J.; Hansen, M.
R.; Andreasen, J. W.; Pisula, W.; Mullen, K.; Cornil, J.; Beljonne, D.
̈
Adv. Mater. 2013, 25, 1939−1947.
(12) Kang, I.; Yun, H.-J.; Chung, D. S.; Kwon, S.-K.; Kim, Y.-H. J.
Am. Chem. Soc. 2013, 135, 14896−14899.
(46) Coropceanu, V.; Cornil, J.; da Silva Filho, D. A.; Olivier, Y.;
́
Silbey, R.; Bredas, J.-L. Chem. Rev. 2007, 107, 926−952.
(13) Li, J.; Zhao, Y.; Tan, H. S.; Guo, Y.; Di, C.-A.; Yu, G.; Liu, Y.;
Lin, M.; Lim, S. H.; Zhou, Y.; Su, H.; Ong, B. S. Sci. Rep. 2012, 2, 754.
(14) Stalder, R.; Mei, J.; Graham, K. R.; Estrada, L. A.; Reynolds, J. R.
Chem. Mater. 2014, 26, 664−678.
(47) Osaka, I.; Abe, T.; Shinamura, S.; Takimiya, K. J. Am. Chem. Soc.
2011, 133, 6852−6860.
(48) Rieger, R.; Beckmann, D.; Mavrinskiy, A.; Kastler, M.; Mullen,
̈
K. Chem. Mater. 2010, 22, 5314−5318.
(15) Mei, J.; Kim, D. H.; Ayzner, A. L.; Toney, M. F.; Bao, Z. J. Am.
Chem. Soc. 2011, 133, 20130−20133.
(49) Lei, T.; Wang, J.-Y.; Pei, J. Chem. Mater. 2014, 26, 594−603.
(50) Mei, J.; Bao, Z. Chem. Mater. 2014, 26, 604−615.
(16) Lei, T.; Cao, Y.; Zhou, X.; Peng, Y.; Bian, J.; Pei, J. Chem. Mater.
2012, 24, 1762−1770.
(17) Lei, T.; Cao, Y.; Fan, Y.; Liu, C.-J.; Yuan, S.-C.; Pei, J. J. Am.
Chem. Soc. 2011, 133, 6099−6101.
(18) Wang, C.; Dong, H.; Hu, W.; Liu, Y.; Zhu, D. Chem. Rev. 2012,
112, 2208−2267.
(19) Li, H.; Kim, F. S.; Ren, G.; Jenekhe, S. A. J. Am. Chem. Soc. 2013,
135, 14920−14923.
(20) Takeda, Y.; Andrew, T. L.; Lobez, J. M.; Mork, A. J.; Swager, T.
M. Angew. Chem., Int. Ed. 2012, 51, 9042−9046.
(21) Lee, J.-K.; Gwinner, M. C.; Berger, R.; Newby, C.; Zentel, R.;
Friend, R. H.; Sirringhaus, H.; Ober, C. K. J. Am. Chem. Soc. 2011, 133,
9949−9951.
(22) Babel, A.; Jenekhe, S. A. J. Am. Chem. Soc. 2003, 125, 13656−
13657.
(23) Zaumseil, J.; Sirringhaus, H. Chem. Rev. 2007, 107, 1296−1323.
(24) Tang, M. L.; Bao, Z. Chem. Mater. 2011, 23, 446−455.
(25) Lei, T.; Dou, J.-H.; Ma, Z.-J.; Liu, C.-J.; Wang, J.-Y.; Pei, J. Chem.
Sci. 2013, 4, 2447−2452.
(26) Chen, H.-Y.; Hou, J.; Zhang, S.; Liang, Y.; Yang, G.; Yang, Y.;
Yu, L.; Wu, Y.; Li, G. Nat. Photon. 2009, 3, 649−653.
(27) Bronstein, H.; Frost, J. M.; Hadipour, A.; Kim, Y.; Nielsen, C.
B.; Ashraf, R. S.; Rand, B. P.; Watkins, S.; McCulloch, I. Chem. Mater.
2013, 25, 277−285.
(28) Park, J. H.; Jung, E. H.; Jung, J. W.; Jo, W. H. Adv. Mater. 2013,
25, 2583−2588.
(29) Lei, T.; Dou, J.-H.; Ma, Z.-J.; Yao, C.-H.; Liu, C.-J.; Wang, J.-Y.;
Pei, J. J. Am. Chem. Soc. 2012, 134, 20025−20028.
(30) Prins, P.; Grozema, F. C.; Schins, J. M.; Patil, S.; Scherf, U.;
Siebbeles, L. D. A. Phys. Rev. Lett. 2006, 96, 146601.
2141
dx.doi.org/10.1021/ja412533d | J. Am. Chem. Soc. 2014, 136, 2135−2141