Anthraquinone derivatives affording n-type organic thin film transistors

Article abstract of DOI:10.1039/b820520e

New anthraquinone derivatives were prepared and used as active layers of organic field-effect transistors (OFETs); these devices showed good n-type characteristics and the quinones were found to be useful for organic semiconductors in OFETs.

Full text of DOI:10.1039/b820520e

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Anthraquinone derivatives affording n-type organic thin film transistorsw
Masashi Mamada,a Jun-ichi Nishida,a Shizuo Tokitob and Yoshiro Yamashita*a
Received (in Cambridge, UK) 17th November 2008, Accepted 9th February 2009
First published as an Advance Article on the web 26th February 2009
DOI: 10.1039/b820520e
New anthraquinone derivatives were prepared and used as active
layers of organic field-effect transistors (OFETs); these devices
showed good n-type characteristics and the quinones were found
to be useful for organic semiconductors in OFETs.
with extension of the p-system. Similarly, the absorption edges
were more red-shifted in 2 and 3 than in 1, suggesting smaller
HOMO–LUMO energy gaps. In the films, the absorption
maxima of 1–3 were observed at 318, 372 and 346 nm,
respectively. The reduction potentials were measured by
differential pulse voltammetry (DPV), and although the
reduction peak of 1 was observed at ꢀ0.88 V vs. SCE, those
of 2 and 3 were not obvious due to their low solubilities. The
LUMO levels of 1–3, calculated by B3LYP/6-311G(d),
were ꢀ3.31, ꢀ3.25 and ꢀ3.43 eV, respectively. This fact shows
that the thiazole ring has a small effect on the LUMO levels.
Single crystals of 1–3 were obtained by sublimation and
X-ray structure analyses were carried out (Fig. 1).z The
molecules of 2 and 3 were almost planar and the dihedral
angles between the component rings were 1.2–2.91 in 2 and
3.1–6.31 in 3. In contrast, the molecule of 1 was more twisted,
with dihedral angles of 33.8–41.81. Fig. 1 displays the packing
structures of 1–3, which exhibit p–p stacking. This is in sharp
contrast with the herringbone structure of the related anthra-
cene derivative.8 The intermolecular distances in the
columns were ca. 3.58 A between the anthraquinone rings in
1, ca. 3.45 A between the thiophene and anthraquinone rings
in 2, and ca. 3.39 A between the thiazole and anthraquinone
rings in 3. This result suggests that the intermolecular inter-
actions along the stacking direction are smaller in 1 than in 2
and 3. These compounds also have intermolecular interactions
along the horizontal direction through quinone–benzene
hydrogen contact.
Organic field-effect transistors (OFETs) are expected to be
critical components in future organic electronics, owing to
their possible applications such as integrated circuits for
flexible electronics.1 In this field, many p-type organic
semiconductors have been developed and their device perfor-
mances are comparable to those of amorphous silicon.2
Considerable efforts have also been taken in the development
of n-type OFETs.3 Perylenediimide derivatives are well-known
as n-type materials that afford high performance OFET
characteristics,4 and some other carbonyl-compounds have
also been used as OFETs in recent years.5 However, quinones
have attracted little attention as organic semiconductors for
OFETs. Although an acene quinone has shown p-type
characteristics, n-type behavior of quinones has not been
reported.6 Quinones have a high electron affinity and various
kinds of derivatives are known. Their preparation is relatively
easy and in addition, it is possible to control the molecular
arrangement by hydrogen bonding through the carbonyl
groups. Therefore, we have now designed anthraquinone
(AQ) derivatives 1–3 to evaluate the potential of quinones as
n-type semiconductors. Trifluoromethylphenyl groups were
introduced as end substituents in them because they effectively
induce n-type behavior.7
Fig. 2 shows X-ray diffractograms (XRD) of the thin films
of 1–3. The XRD patterns were independent of the prepara-
tion conditions and were not consistent with the simulated
patterns based on the single-crystal structures. Therefore, the
thin film structures are considered to be different from those of
single crystals. The reflection peak corresponding to the
molecular arrangement perpendicularly standing on the
substrate was observed only in 3, but was very weak. Other
reflection peaks were observed at higher 2y with low intensities
but the interpretation of the peaks is still puzzling.
Scheme 1 shows the synthesis of anthraquinones 1–3.
These compounds were prepared more easily than a related
anthracene derivative, which was reported as an n-type
semiconductor.8 The compounds were purified by sublima-
tion, and characterized by MS, single crystal X-ray analysis
and elemental analysis.
Differential scanning calorimetry (DSC) measurements of
1–3 exhibited sharp melting peaks at 320, 347 and 379 1C,
respectively, and absorption maxima were observed at 278,
364 and 349 nm in dichloromethane, which were red-shifted
Fig. 3 shows tapping mode atomic-force microscopy (AFM)
images of thin films of 1–3. The film of 1 consists of layers of
large grains with a flat surface, while on the other hand, the
films of 2 and 3 are composed of smaller grains. Although the
a Tokyo Institute of Technology, Interdisciplinary Graduate School of
Science and Engineering, Department of Electronic Chemistry,
4259 Nagatsuta, Midori-ku, Yokohama 226-8502, Japan.
E-mail: yoshiro@echem.titech.ac.jp; Fax: +81 45-924-5489;
Tel: +81 45-924-5571
b NHK Science & Technical Research Laboratories, 1-10-11 Kinuta,
Setagaya-ku, Tokyo 157-8510, Japan
w Electronic supplementary information (ESI) available: Synthesis,
absorption spectra, DPV, DFT calculations and X-ray crystallo-
graphic data for 1–3, XRD pattern of the film, AFM measurement
of the film, and FET data for the bottom and top contact devices.
CCDC 709632–709634. For ESI and crystallographic data in CIF or
other electronic format, see DOI: 10.1039/b820520e
Scheme 1 The synthesis of AQ derivatives.
Chem. Commun., 2009, 2177–2179 | 2177
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Fig. 3 The surface morphologies of 50 nm films of (a) 1, (b) 2 and
(c) 3 deposited on HMDS-treated SiO2 at 50 1C.
Table 1 The FET characteristics of devices based on 1–3
Mobility/
On : off
Fig. 1 (a) View of packing as seen down the long molecular axis in 1.
(b) Packing structure of 2 along the b-axis. (c) Packing structure of 3
along the c-axis.
Compound
Contact
cm2 Vꢀ1 sꢀ1 ratio
Threshold/V
1
Bottoma
Topb
7.0 ꢂ 10ꢀ4
1.2 ꢂ 10ꢀ4
0.020
0.005
0.074
0.067
7 ꢂ 104 37
2 ꢂ 102 32
2
3
Bottomc
Topb
6 ꢂ 102 26
1 ꢂ 104 26
1 ꢂ 104 25
3 ꢂ 105 21
Bottomc
Topb
a
SiO2: 300 nm, L/W = 50/294000, S/D electrodes: Cr(10 nm)/Au(20 nm).
c
SiO2: 200 nm, L/W = 50/1000, S/D electrodes: Au(50 nm). SiO2:
b
300 nm, L/W = 50/500, S/D electrodes: Cr(10 nm)/Au(20 nm).
had silanol groups at the SiO2 surface since piranha clean was
carried out. The acidic hydrogens of the silanol groups might
have been coordinated to the carbonyl groups of the quinones,
resulting in the formation of carrier traps. Therefore, passiva-
tion of the active surface would be important in the quinone
systems.
The OFET devices based on 1 showed moderate mobilities,
which were slightly lower than those of the corresponding
anthracene derivative; however the threshold voltages were
much lower.8 It should be noted that anthraquinone 1 showed
semiconducting behavior, although the effective conjugation
length was short compared to usual semiconductors of
OFETs. The FET characteristics were improved in films of 2
and 3 due to the increased conjugation length, as well as to the
enhanced intermolecular interactions. The devices of 3 showed
better performances (Fig. 4) than those of 2 and this result can
be attributed to the difference in intermolecular interactions or
film morphologies, as suggested in XRD and AFM measure-
ments. The mobility of 3 was increased to 0.18 cm2 Vꢀ1 sꢀ1
(on : off ratio: 105, threshold voltage: 40 V) when a higher
drain voltage (VD = 100 V) was applied.
Fig. 2 X-Ray diffractograms of 50 nm films of (a) 1, (b) 2 and (c) 3
deposited on HMDS-treated SiO2 at 50 1C.
grains of 2 and 3 are plate-like, similar to those of 1, each grain
is not lamellarly stacked, resulting in a rough surface. The
grain sizes are larger and the surface is more smooth in 3
than in 2.
The OFET devices were fabricated under several conditions
and the characteristics of films deposited on HMDS-treated
substrate at 50 1C are summarized in Table 1. Top contact
devices generally showed higher performances than bottom
contact ones because of better contacts between the electrodes
and semiconductors in the former devices. In this case,
however, the devices with bottom contact configuration had
a tendency to show higher mobilities. This fact suggests that
the anthraquinones have good contacts with electrodes,
even in bottom contact devices. The top contact devices
without HMDS treatment exhibited low mobilities
(10ꢀ3–10ꢀ5 cm2 Vꢀ1 sꢀ1 for 3). Our bare-top contact devices
In summary, we have developed n-type FET devices based
on novel anthraquinones for the first time as quinones.
Although quinones have been considered to work in electron
trapping, these findings have proved that quinones can afford
high performance n-type FET devices. Since quinone units can
be easily incorporated to p-conjugated systems, they would be
useful as a core of n-type semiconductors for OFETs.
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crystallographic data in CIF or other electronic format, see DOI:
10.1039/b820520e.
1 (a) M. Muccini, Nat. Mater., 2006, 5, 605; (b) L. Zhou, A. Wanga,
S.-C. Wu, J. Sun, S. Park and T. N. Jackson, Appl. Phys. Lett., 2006,
88, 083502; (c) T. D. Anthopoulos, S. Setayesh, E. Smits, M. Colle,
¨
E. Cantatore, B. de Boer, P. W. M. Blom and D. M. de Leeuw, Adv.
Mater., 2006, 18, 1900; (d) T. Sekitani, M. Takamiya, Y. Noguchi,
S. Nakano, Y. Kato, T. Sakurai and T. Someya, Nat. Mater., 2007,
6, 413; (e) D. R. Hines, V. W. Ballarotto and E. D. Williams,
J. Appl. Phys., 2007, 101, 024503; (f) S. Ju, A. Facchetti, Y. Xuan,
J. Liu, F. Ishikawa, P. Ye, C. Zhou, T. J. Marks and D. B. Janes,
Nat. Nanotechnol., 2007, 2, 378.
2 (a) M. Halik, H. Klauk, U. Zschieschang, G. Schmid,
S. Ponomarenko, S. Kirchmeyer and W. Weber, Adv. Mater.,
2003, 15, 917; (b) M. M. Payne, S. R. Parkin, J. E. Anthony,
C. C. Kuo and T. N. Jackson, J. Am. Chem. Soc., 2005, 127, 4986;
(c) A. L. Briseno, S. C. B. Mannsfeld, M. M. Ling, S. Liu,
R. J. Tseng, C. Reese, M. E. Roberts, Y. Yang, F. Wudl and
Z. Bao, Nature, 2006, 444, 913; (d) T. Yamamoto and K. Takimiya,
J. Am. Chem. Soc., 2007, 129, 2224; (e) T. Izawa, E. Miyazaki and
K. Takimiya, Adv. Mater., 2008, 20, 3388.
Fig. 4 (a) Output characteristics and (b) transfer characteristics of
films of 3 deposited on HMDS-treated SiO2 at 50 1C with top contact
configuration.
This work was supported by a Grant-in-Aid for Scientific
Research (no. 19350092) from the Ministry of Education,
Culture, Sports, Science and Technology, Japan, the Mizuho
Foundation for the Promotion of Sciences, and the Global
COE program ‘‘Education and Research Center for
Emergence of New Molecular Chemistry’’. The author would
like to thank Dr M. Yamasaki (Rigaku Co., Ltd.) for help
with the X-ray structure analysis.
3 (a) A. Facchetti, Mater. Today, 2007, 10, 28; (b) A. R. Murphy and
J. M. J. Frechet, Chem. Rev., 2007, 107, 1066.
4 (a) R. J. Chesterfield, J. C. McKeen, C. R. Newman, P. C. Ewbank,
D. A. da S. Filho, J. L. Bredas, L. L. Miller, K. R. Mann and C. D.
J. Frisbie, J. Phys. Chem. B, 2004, 108, 19281; (b) B. A. Jones,
M. J. Ahrens, M.-H. Yoon, A. Facchetti, T. J. Marks and
M. R. Wasielewski, Angew. Chem., Int. Ed., 2004, 43, 6363;
(c) H. Z. Chen, M. M. Ling, X. Mo, M. M. Shi, M. Wang and
Z. Bao, Chem. Mater., 2007, 19, 816; (d) R. Schmidt, M. M. Ling,
J. H. Oh, M. Winkler, M. Konemann, Z. Bao and F. Wurthner,
Adv. Mater., 2007, 19, 3692; (e) R. T. Weitz, K. Amsharov,
U. Zschieschang, E. B. Villas, D. K. Goswami, M. Burghard,
H. Dosch, M. Jansen, K. Kern and H. Klauk, J. Am. Chem. Soc.,
2008, 130, 4637.
5 (a) M.-H. Yoon, S. A. DiBenedetto, A. Facchetti and T. J. Marks,
J. Am. Chem. Soc., 2005, 127, 1348; (b) J. A. Letizia, A. Facchetti,
C. L. Stern, M. A. Ratner and T. J. Marks, J. Am. Chem. Soc., 2005,
127, 13476; (c) T. Nakagawa, D. Kumaki, J. Nishita, S. Tokito and
Y. Yamashita, Chem. Mater., 2008, 20, 2615; (d) H. Usta,
A. Facchetti and T. J. Marks, Org. Lett., 2008, 10, 1385; (e) Y. Ie,
Y. Umemoto, M. Okabe, T. Kusuniki, K. Nakayama, Y.-J. Pu,
J. Kido, H. Tada and Y. Aso, Org. Lett., 2008, 10, 833.
Notes and references
z The X-ray measurements of 1–3 were performed on a Rigaku
R-AXIS RAPID imaging plate diffractometer with Mo-Ka radiation
(l = 0.71075 A) at ꢀ180 1C. The structures were solved by the direct
method (SIR97) and refined by the full-matrix least-squares method
on F2 with anisotropic temperature factors for non-hydrogen atoms.
Hydrogen atoms were refined using the riding model and absorption
correction was applied using an empirical procedure. Crystal data for
1: C28H14F6O2, M = 496.41, crystal dimensions 0.50 ꢂ 0.50 ꢂ 0.05 mm,
monoclinic, space group P21/n, a = 8.1535(2), b = 8.1662(3),
c = 31.2347(9) A, b = 91.7150(9)1, V = 2078.77(11) A3, Z = 4, Dc =
1.586 g cmꢀ3, 19 754 reflections collected, 4761 independent (Rint
=
0.026), GOF = 1.059, R1 = 0.0394, wR2 = 0.1104 for all reflections.
CCDC reference number 709632. Crystal data for 2: C36H18F6O2S2,
M = 660.65, crystal dimensions 0.60 ꢂ 0.15 ꢂ 0.10 mm, triclinic,
space group P-1, a = 7.7033(15), b = 10.4109(19), c = 17.980(3) A,
a = 73.309(4), b = 84.213(5), g = 78.391(5)1, V = 1351.5(4) A3, Z = 2,
Dc = 1.623 g cmꢀ3, 10 827 reflections collected, 4924 independent
(Rint = 0.085), GOF = 0.964, R1 = 0.0823, wR2 = 0.2558 for all
reflections. This R1 is for the observed 2430 reflections. CCDC
reference number 709633. Crystal data for 3: C34H16F6O2N2S2,
M = 662.62, crystal dimensions 0.30 ꢂ 0.25 ꢂ 0.10 mm, triclinic,
space group P-1, a = 12.2445(11), b = 13.2130(10), c = 14.4529(14) A,
a = 73.124(2), b = 73.488(2), g = 65.1720(18)1, V = 1995.0(3) A3,
Z = 3, Dc = 1.654 g cmꢀ3, 16 127 reflections collected, 7118
6 Q. Miao, M. Lefenfeld, T.-Q. Nguyen, T. Siegrist, C. Kloc and
C. Nuckolls, Adv. Mater., 2005, 17, 407.
7 (a) S. Ando, R. Murakami, J. Nishida, H. Tada, Y. Inoue, S. Tokito
and Y. Yamashita, J. Am. Chem. Soc., 2005, 127, 14996;
(b) K. Takimiya, Y. Kunugi, H. Ebata and T. Otsubo, Chem. Lett.,
2006, 35, 1200; (c) T. Yasuda, M. Saito, H. Nakamura and
T. Tsutsui, Appl. Phys. Lett., 2006, 89, 182108; (d) T. Kojima,
J. Nishida, S. Tokito, H. Tada and Y. Yamashita, Chem. Commun.,
2007, 14, 1430; (e) M. Mamada, J. Nishida, D. Kumaki, S. Tokito
and Y. Yamashita, Chem. Mater., 2007, 19, 5404.
independent (Rint = 0.056), GOF = 0.955, R1 = 0.0590, wR2 =
0.1736 for all reflections. CCDC reference number 709634. For
8 S. Ando, J. Nishida, E. Fujiwara, H. Tada, Y. Inoue, S. Tokito and
Y. Yamashita, Chem. Mater., 2005, 17, 1261.
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Chem. Commun., 2009, 2177–2179 | 2179