Synthesis and n-type field-effect transistor characteristics of dioxopyrrolopyrrole derivatives

Article abstract of DOI:10.1246/cl.2011.822

Dioxopyrrolopyrrole derivatives with electron-withdrawing groups have been synthesized and applied to organic field-effect transistors as n-channel semiconductors. A derivative with an intermolecular hydrogen-bonding network showed a good electron mobility up to 2.9 10¹2 cm2V ¹1 s¹1.

Full text of DOI:10.1246/cl.2011.822

doi:10.1246/cl.2011.822
822
Published on the web July 2, 2011
Synthesis and n-Type Field-effect Transistor Characteristics
of Dioxopyrrolopyrrole Derivatives
Yuki Suna,1 Jun-ichi Nishida,1 Yoshihide Fujisaki,2 and Yoshiro Yamashita*1
1Department of Electronic Chemistry, Interdisciplinary Graduate School of Science and Engineering,
Tokyo Institute of Technology, G1-8, 4259 Nagatsuta, Midori-ku, Yokohama, Kanagawa 225-8502
2NHK Science and Technical Research Laboratories, Kinuta, Setagaya-ku, Tokyo 157-8510
(Received May 20, 2011; CL-110427; E-mail: yoshiro@echem.titech.ac.jp)
Dioxopyrrolopyrrole derivatives with electron-withdrawing
groups have been synthesized and applied to organic field-effect
transistors as n-channel semiconductors. A derivative with
an intermolecular hydrogen-bonding network showed a good
¹1
electron mobility up to 2.9 © 10¹2 cm2 V¹1 s
.
n-Type organic semiconductors for organic field-effect
transistors (OFETs) have attracted considerable attention for
the fabrication of complementary logic circuits.1 However, the
development of high-performance ambient-stable n-type materi-
als has lagged behind that of p-type materials due to the inherent
instability of organic anions toward oxygen and water.
Dioxopyrrolopyrrole (DPP) consisting of a fused hetero-
cycle possesses a planar ³-electron core and two amide groups.
DPP derivatives have been used as high-performance organic
pigments with brilliant red color.2 Recently, DPP-based small
molecules have been attracting much attention as materials for
organic electronics because of their promising charge trans-
porting performance in solar cells as well as OFETs.3,4 The
formation of multiple hydrogen-bonding networks between the
amide groups is a particularly noteworthy characteristic of DPP.
This strong intermolecular interaction makes DPPs into environ-
mentally stable pigments which can be widely used in industry.
This is also attractive for high-performance n-type materials
because a close-packed crystal structure with hydrogen bonding
enhances electron hopping between the molecules.5 Although
only one DPP-based small molecule with a hydrogen-bonding
network was reported to show FET characteristics, it shows
Scheme 1. Synthesis of DPP derivatives.
Table 1. Summary of photophysical properties of DPP deriv-
atives
Solutiona
abs/nm em/nm
514, 479 530, 566 538, 494
486 546 502
582, 540 598, 652 514, 609
596, 554 622, 672 533, 640
Film
-abs/nm Solution Film
Egopt b/eV
Compound
-
-
1
2
3
4
2.31
2.53
2.03
2.00
2.07
2.15
1.75
1.65
b
aObtained in 1 © 10¹5 M THF solution. Determined from the
onset of electronic absorption wavelength: Egopt = 1240/
- (nm).
¹5
p-type behavior with moderate mobility of 1.43 © 10
bonded N-H are observed within the range of 2700 to
3200 cm¹1. In the hydrogen-bonded DPP crystals, ³-³ inter-
actions exist along the stacking direction of molecules and four
intermolecular hydrogen bonds per molecule between the NH
group of one molecule and the oxygen atom of the neighboring
one horizontally extend to the molecular plane. Although the
single crystals of 1 and 3 could not be obtained, such a
hydrogen-bonding network is commonly observed in DPP
crystals and contributes to the large red-shifts in the spectra of
DPP solids compared with those in solution.7
The photophysical and electrochemical properties of DPPs
are summarized in Table 1. The UV-vis spectrum of 1 in the
film is red-shifted compared with that in solution due to the
strong intermolecular ³-³ interaction and hydrogen bonding. In
the case of 2, disappearance of vibronic structure and a large
Stokes shift in its fluorescence spectrum (60 nm) (Figure S29)
were observed, indicating loss of the molecular planarity due
to the steric interaction between the methyl group and the
neighboring phenyl ring. The distortion from planarity caused
by N-substitution reduces the overlap between the ³-orbitals of
¹1 4b
cm2 V¹1 s
.
We report here the first examples of n-type semiconducting
small molecular DPP derivatives. We introduced trifluoro-
methylphenyl (CF3Ph) groups onto the DPP core. The CF3Ph
group is expected to provide DPP with a low-lying LUMO level
suitable for electron transport.6 We have also investigated the
effects of the hydrogen-bonding network between the DPP
molecules on the semiconducting properties.
DPP derivatives possessing CF3Ph groups and hydrogen-
bonding sites were synthesized as shown in Scheme 1. For
comparison, N-methyl-substituted DPP derivatives that cannot
form intermolecular hydrogen-bonding networks were also
synthesized. IR spectroscopy (Figure S19) confirmed the for-
mation of N-H£O hydrogen bonding between the amide
hydrogen atoms and the carbonyl oxygen atoms. In the spectra
of N-methyl derivatives 2 and 4, the free-carbonyl stretching
vibration was observed at 1670 and 1661 cm¹1, respectively.
¹1
These bands shift to 1640 and 1634 cm
in 1 and 3,
respectively, where multiple peaks assigned to the hydrogen-
Chem. Lett. 2011, 40, 822-824
© 2011 The Chemical Society of Japan
www.csj.jp/journals/chem-lett/

823
Table 2. FET characteristics of DPP derivativesa
Mobility
Compound
Tsub/°C
Type Ion/Ioff Vth/V
¹1
/cm2 V¹1 s
¹3
1
rt
100
rt
rt
100
rt
9.2 © 10
2.9 © 10
3.7 © 10
6.9 © 10
7.9 © 10
1.4 © 10
9.6 © 10
9.3 © 10
1.3 © 10
n
n
n
n
n
n
p
n
p
8 © 103
18
16
23
43
37
37
¹36
34
¹2
4 © 102
¹6
¹5
¹3
¹4
¹6
¹4
¹5
2
3
20
4 © 104
Figure 2. X-ray diffractograms of film 1 (left) and 2 (right)
vapor-deposited on HMDS-treated SiO2 at Tsub = 100 °C.
5 © 104
4
20
7
5
100
2
¹45
aDeposition temperature (Tsub), field-effect mobility, current
on/off ratio (Ion/Ioff), and threshold voltage (Vth) for vapor-
deposited films of DPP derivatives on HMDS-treated SiO2.
Figure 3. Surface morphology of film of 1 deposited onto
HMDS-treated Si/SiO2 at Tsub = 100 °C.
lity decreased one order of magnitude. Generally, field-effect
mobilities are expected to increase on the top-contact/bottom-
gate (TC/BG) configuration device compared with the BC/BG
device. Nevertheless, the electron mobility of 1 measured on a
TC/BG configuration device was 2.0 © 10¹2 cm2 V¹1 s¹1 which
is almost the same as that on the BT/BG configuration device.
The films of DPP derivatives deposited on SiO2/Si
substrates were investigated by X-ray diffraction in a reflection
mode. Sharp reflections up to the third order were observed
on the film of 1 (Figure 2), indicating formation of lamellar
ordering and high crystallinity of 1 on the substrate. The
d-spacing obtained from the first reflection peak (2ª = 5.06°) is
17.5 ¡. Since the molecular length of 1 obtained from the
calculations is 16.2 ¡, this molecule is thought to be almost
perpendicular to the substrate. This is an ideal molecular
arrangement for charge transport in most bottom-gate OFET
configurations. No clear peak was observed on the film of 2 due
to its low crystallinity (Figure 2).
As shown in AFM images of film 1 (Figure 3), large grains
grew in the film. The height of grains reaches approximately
200 nm and the surface of the film is very rough. This roughness
would disturb the contact between the active layer and the
electrode in the TC/BG configuration device, which may be the
reason for no improved electron mobility.
In summary, we have synthesized DPP derivatives possess-
ing CF3Ph groups with low LUMO energies and demonstrated
that they act as n-type materials on FETs with a good mobility
up to 2.9 © 10¹2 cm2 V¹1 s¹1. The hydrogen-bonding network
leads to high crystallinity and well-ordered films, resulting in
good electron transporting behavior. This suggests that incor-
porating hydrogen-bonding networks is valid to create high-
performance n-type materials.
Figure 1. Output characteristic curves (a) and transfer charac-
teristic curves (b) for FET 1 vapor-deposited on HMDS-treated
SiO2 substrates at Tsub = 100 °C.
DPP core.8 The UV-vis spectra of 3 and 4 are red-shifted
compared with those of 1 and 2 in solution due to the extended
³-conjugation and the donor-acceptor interaction. The relatively
small Stokes shift in fluorescence spectrum of 4 indicates that
the steric interaction between the methyl group and the
neighboring thiophene ring is small and consequently distortion
of the compound is insignificant. The absorption onset wave-
length of the 4 film in which no intermolecular hydrogen
bonding exist is longer than that of the 3 film. This suggests that
the donor-acceptor interaction is stronger than the hydrogen
bonding within the molecules. Cyclic voltammograms of 1 and 2
show the first reduction peaks at ¹0.83 and ¹0.86 V (vs. SCE),
respectively (Figure S49). The LUMO levels estimated from the
first reduction potentials are low enough for efficient electron
injection into the semiconductors. CV measurements could not
be performed on 3 and 4 due to their low solubility. The
calculated LUMO levels of them are ¹3.50 and ¹3.40 eV,
respectively (Figure S99). These values are slightly lower than
those of 1 and 2.
The field-effect mobilities measured on a bottom-contact/
bottom-gate (BC/BG) configuration device under vacuum are
shown in Table 2. The highest electron mobility of 2.9 ©
¹1
10¹2 cm2 V¹1 s was obtained in 1 deposited at Tsub = 100 °C
(Figure 1). The mobility decreased by four orders of magnitude
in the film of 2 in which no hydrogen-bonding network was
formed. DPP 3 with thiophene units also exhibited good electron
mobilities up to 7.9 © 10¹3 cm2 V¹1 s¹1. In N-methyl derivative
4, ambipolar behavior with a moderate hole mobility (up to
1.3 © 10¹5 cm2 V¹1 s¹1) was observed while the electron mobi-
References and Notes
1
E. J. Meijer, D. M. de Leeuw, S. Setayesh, E.
van Veenendaal, B.-H. Huisman, P. W. M. Blom, J. C.
Hummelen, U. Scherf, T. M. Klapwijk, Nat. Mater. 2003, 2,
Chem. Lett. 2011, 40, 822-824
© 2011 The Chemical Society of Japan
www.csj.jp/journals/chem-lett/

824
678.
J. Am. Chem. Soc. 2005, 127, 5336. c) S. Ando, R.
Murakami, J. Nishida, H. Tada, Y. Inoue, S. Tokito, Y.
Yamashita, J. Am. Chem. Soc. 2005, 127, 14996. d) D.
Kumaki, S. Ando, S. Shimono, Y. Yamashita, T. Umeda, S.
Tokito, Appl. Phys. Lett. 2007, 90, 053506. e) T. Kono, D.
Kumaki, J. Nishida, T. Sakanoue, M. Kakita, H. Tada, S.
Tokito, Y. Yamashita, Chem. Mater. 2007, 19, 1218. f) T.
Kono, D. Kumaki, J. Nishida, S. Tokito, Y. Yamashita,
Chem. Commun. 2010, 46, 3265. g) K. Takimiya, Y. Kunugi,
H. Ebata, T. Otsubo, Chem. Lett. 2006, 35, 1200. h) H.
Wang, Y. Wen, X. Yang, Y. Wang, W. Zhou, S. Zhang, X.
Zhan, Y. Liu, Z. Shuai, D. Zhu, ACS Appl. Mater. Interfaces
2009, 1, 1122.
2
3
O. Wallquist, R. Lenz, Macromol. Symp. 2002, 187, 617.
a) J. Mei, K. R. Graham, R. Stalder, S. P. Tiwari, H. Cheun,
J. Shim, M. Yoshio, C. Nuckolls, B. Kippelen, R. K.
Castellano, J. R. Reynolds, Chem. Mater. 2011, 23, 2285. b)
P. Sonar, G.-M. Ng, T. T. Lin, A. Dodabalapur, Z.-K. Chen,
J. Mater. Chem. 2010, 20, 3626. c) B. Walker, A. B. Tamayo,
X.-D. Dang, P. Zalar, J. H. Seo, A. Garcia, M. Tantiwiwat,
T.-Q. Nguyen, Adv. Funct. Mater. 2009, 19, 3063. d) A. B.
Tamayo, X.-D. Dang, B. Walker, J. Seo, T. Kent, T.-Q.
Nguyen, Appl. Phys. Lett. 2009, 94, 103301. e) M.
Tantiwiwat, A. Tamayo, N. Luu, X.-D. Dang, T.-Q.
Nguyen, J. Phys. Chem. C 2008, 112, 17402.
4
5
6
a) S.-L. Suraru, U. Zschieschang, H. Klauk, F. Würthner,
Chem. Commun. 2011, 47, 1767. b) H. Yanagisawa, J.
Mizuguchi, S. Aramaki, Y. Sakai, Jpn. J. Appl. Phys. 2008,
47, 4728.
a) Q. Tang, Z. Liang, J. Liu, J. Xu, Q. Miao, Chem.
Commun. 2010, 46, 2977. b) M. Gsänger, J. H. Oh, M.
Könemann, H. W. Höffken, A.-M. Krause, Z. Bao, F.
Würthner, Angew. Chem., Int. Ed. 2010, 49, 740.
7
8
9
a) J. Mizuguchi, J. Phys. Chem. A 2000, 104, 1817. b) J.
Mizuguchi, A. Grubenmann, G. Rihs, Acta Crystallogr.,
Sect. B 1993, 49, 1056. c) J. Mizuguchi, A. Grubenmann, G.
Wooden, G. Rihs, Acta Crystallogr., Sect. B 1992, 48, 696.
a) M. Vala, J. Vyňuchal, P. Toman, M. Weiter, S. Luňák, Jr.,
Dyes Pigm. 2010, 84, 176. b) M. Vala, M. Weiter, J.
Vyňuchal, P. Toman, S. Luňák, Jr., J. Fluoresc. 2008, 18,
1181.
a) S. Ando, J. Nishida, E. Fujiwara, H. Tada, Y. Inoue, S.
Tokito, Y. Yamashita, Chem. Mater. 2005, 17, 1261. b) S.
Ando, J. Nishida, H. Tada, Y. Inoue, S. Tokito, Y. Yamashita,
Supporting Information is available electronically on the
CSJ-Journal Web site, http://www.csj.jp/journals/chem-lett/
index.html.
Chem. Lett. 2011, 40, 822-824
© 2011 The Chemical Society of Japan
www.csj.jp/journals/chem-lett/