Birhodanines and their sulfur analogues for air-stable n-channel organic transistors

Article abstract of DOI:10.1039/c7tc02886e

A series of thin-film n-channel organic field-effect transistors based on various birhodanines, 3,3′-dialkyl-5,5′-bithiazolidinylidene-2,2′-dione-4,4′-dithiones (OS-R) and their sulfur analogues, 3,3′-dialkyl-5,5′-bithiazolidinylidene-2,4,2′,4′-tetrathiones (SS-R) are studied. The SS-R compounds have tilted stacking crystal structures, whereas the OS-R compounds show basically herringbone structures. The alkyl chain R length and the intermolecular S-S interactions influence the molecular packing to realize excellent long-term air stability in the thin-film transistors.

Full text of DOI:10.1039/c7tc02886e

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Fine-tuning of gold nanorod dimensions and plasmonic properties using
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ARTICLE
Birhodanines and their sulfur analogues for air-stable
n-channel organic transistors†
Cite this: DOI: 10.1039/x0xx00000x
Kodai Iijima,a Yann Le Gal,b Toshiki Higashino,ac Dominique Lorcy,b and
Takehiko Mori*a
Received 00th January 2017,
Accepted 00th January 2017
A series of thin-film n-channel organic field-effect transistors based on various birhodanines, 3,3'-dialkyl-
5,5'-bithiazolidinylidene-2,2'-dione-4,4'-dithiones (OS-
bithiazolidinylidene-2,4,2',4'-tetrathiones (SS- ) are studied. The SS-
crystal structures, whereas the OS- compounds show basically herringbone structures. The alkyl chain R
R
) and their sulfur analogues, 3,3'-dialkyl-5,5'-
DOI: 10.1039/x0xx00000x
R
R
compounds have tilted stacking
R
www.rsc.org/
length and the intermolecular S-S interactions influence the molecular packing to realize excellent long-
term air stability in the thin-film transistors.
performance. Being aware of the importance to keep a balance
between solubility, crystallinity, and close intermolecular
Introduction
There has been significant progress in the development of high-
performance organic transistors.1,2 However, it is still
comparatively difficult to attain air-stability in electron-
transporting (n-channel) transistors in contrast to hole-
transporting (p-channel) transistors.3 High-performance p-
channel organic transistors have been realized using such
molecules as benzothienobenzothiophene,2,4 but there remains a
lot of room for improvement in n-channel materials.3 Recently,
high-performance organic semiconductors have been developed
in donor-acceptor polymers,1 where thiophene backbone is
widely used as the donor part, but a variety of units such as
benzothiadiazole, naphthalene diimide, diketopyrrolopyrrole,
and isoindigo, have been investigated as the acceptor part.
We have previously reported good performance and excellent
air stability of n-channel organic transistors based on a sulfur rich
electron acceptor, 3,3'-diethyl-5,5'-bithiazolidinylidene-2,4,2',4'-
tetrathione (SS-Et in Scheme 1), particularly in the single-crystal
transistors.5 The excellent air stability has been ascribed to the
extensive three dimensional S-S interactions. In order to have
better understanding on the observed performance and to
evaluate the role of the S-S interactions, we have decided to
investigate alternative acceptor analogues represented in Scheme
1, where the outer thiocarbonyl (=S) groups are replaced by
either dicyanomethylene moieties (S(CN)2-Et) or carbonyl (=O)
interactions, we have examined acceptors with R = methyl (Me),
ethyl (Et), n-propyl (Pr), and n-butyl (Bu) groups. Herein, we
report a systematic study of these -acceptors as thin-film n-
channel organic transistor materials.
Scheme 1. Molecular structures, where R = methyl (Me), ethyl (Et), n-
propyl (Pr), and n-butyl (Bu).
Results and discussion
Synthesis and electronic properties
The preparation of the SS-
trapping of the dithiolate generated from 18 as a titanocene
complex was
(Scheme 2).9,10 The titanocene complex
converted to in the presence of triphosgene, and the
dimerization into SS- was realized by simply heating in
refluxing toluene as described in Ref. 10. S(CN)2-Et 11 SO-Et 10
and OS-
(R = Me, Et, Pr, and Bu)12 were prepared
R derivatives involves first the
moieties (SO-
R). Alternatively, the inner thiocarbonyl groups
2
2
are replaced by carbonyl moieties in OS-
R.
The latter
3
derivatives can be considered as rhodanine dimers or 5,5'-
birhodanines,6 the component of which is an important unit in
pharmacy and dyes.7 We have also extended our study to
acceptors bearing different N-alkyl chains to investigate the
influence to the molecular packing and the transistor
R
3
,
,
R
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Table 1. Redox potentials, energy levels, and optical gaps.
E11/2 (V)
E21/2 (V)
ELUMO (eV)a

edge (eV)
Optical gap (eV)
EHOMO (eV)a
SS-Me
-0.55
-0.57
-0.58
-0.40
-0.82
-0.99
-1.00
-1.00
-1.00
−0.94
−4.25
604
609
610
632
494
478
481
482
482
2.05
2.04
2.03
1.96
2.51
2.59
2.58
2.57
2.57
−6.30
SS-Pr
−1.03
−4.23 (−4.22)
−4.22
−6.27 (−6.64)
−6.25
SS-Bu
S(CN)2-Et
SO-Et
−1.00
−0.83
−4.4 (−4.68)
−3.9 (−3.81)
−3.81
−6.38 (−7.06)
−6.49 (−6.70)
−6.40
−1.26
OS-Me
OS-Et
-
-
-
-
−3.80 (−3.59)
−3.81
−6.38 (−6.60)
−6.37
OS-Pr
OS-Bu
−3.81
−6.37
a The LUMO levels were estimated by assuming the reference energy level of ferrocene/ferrocenium to be 4.8 eV from the vacuum
level.15 The HOMO levels were obtained from the LUMO levels and the optical gaps. The values in the parentheses were from the
Gaussian 09 calculation at the B3LYP/6-311G(d,p) level.17
SS-Et9
around 2 eV (Table 1) with the smallest one observed for
S(CN)2-Et and the largest one for OS- Accordingly, the
< . The optical gaps are estimated to be
S(CN)2-Et 11
R.
highest occupied molecular orbital (HOMO) levels are expected
to be located below -6.0 eV. These experimental estimations of
HOMO and LUMO levels are in agreement with the molecular
orbital calculations (Table 1).
Scheme 2. i 1) LDA, 2) S8, 3) Cp2TiCl2, ii (Cl3CO)2CO, iii toluene, .
according to the literature. It should be noted that the synthesis
of OS- is a one-step reaction of the corresponding amine with
R
carbon disulfide and dimethyl acetylene dicarboxylate at room
temperature (Scheme 2).12 Alternatively, the carbamates13 were
reacted with dimethyl acetylene dicarboxylate to give OS-R 14
Frontier orbital energy levels of these acceptors are estimated
by cyclic voltammetry. The cyclic voltammograms of SS-
S(CN)2-Et and SO-Et exhibit two well defined reversible
reduction waves while OS- show only one reversible reduction
wave (Figs. 1(a) and (b)). From the first reduction potentials, the
lowest unoccupied molecular orbital (LUMO) levels (ELUMO
were estimated as shown in Table 1.15 SS-
show the LUMO
.
R,
R
)
R
levels located below -4.0 eV, indicating strong enough acceptor
ability to achieve air-stable electron-transporting properties.16
Comparison of the LUMO levels of the R = Et acceptors shows
Figure 1. Cyclic voltammograms of (a) SS-R and S(CN)2-Et, and (b)
SO-Et and OS-R. Absorption spectra of (c) SS-R and S(CN)2-Et, and
a decrease of the accepting ability in the order of S(CN)2-Et11
SS-Et9
SO-Et OS-Et. The LUMO levels of SO-Et and OS-
are located slightly above -4.0 eV. These observations find
>
(d) SO-Et and OS-R
.
>
>
R
Transistor characteristics
their origin in the LUMO shape which is predominantly located
on the central fragment involving the inner thiocarbonyl or
carbonyl moieties while weaker contributions are found on the
outer thiocarbonyl or carbonyl groups (Fig. S1).9,10
The optical gaps are estimated from the solution absorption
spectra (Figs. 1(c) and (d)). A bathochromic shift of about 150
nm is observed for the absorption maximum from 481 nm for
OS-Et to 632 nm for S(CN)2-Et in the order OS-Et < SO-Et <
Thin film transistors with bottom-gate top-contact configuration
were prepared by vacuum evaporation of the acceptors on a
tetratetracontane (TTC)-treated SiO2/Si substrate (300 nm
SiO2).18 Gold was used as source and drain electrodes. The
transistor characteristics were measured under vacuum and
2 | J. Name., 2012, 00, 1-3
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Table 3. Crystallographic data, thin-film XRD d values, and the tilt angles from the substrate normal.
Table 2. Transistor characteristics of the thin-film transistors.
After storage
Measurement
μ
(cm2 V−1 s−1
μ
(cm2 V−1 s−1
averaOgeS-Et
)
Vth (V)
on/off ratio
SS-Me
SS-Prmax
OS-Me
OS-Pr
OS-Bu
)
Formula
Formula weight
Crystal System
Space Group
Shape
C8H N2S6
C H14N2S
C H N O S
C10H10N2O2S−5 C12H14N2O2S4
7.2×104
C14H18N2O2S4
374.55
−5
un6der vacuum 12
6 7.3×10 6
10
30
12
31
17
11
17
13
34
38
4
6×101
2×103
8
2
2
4
SS-Me
SS-Et
SS-Pr
−5
322.51
378.62
2−950.39
4.6×10
318.44
346.49
monoclinic
P21/c
in air
3.4×10
under vacuum
monoclinic
1.5×10−2
5.9×10−3
6×103
triclinic
orthorhombic
orthorhombic
Pbca
in air
1.2×10−2
P-1
4.6×10−3
4×103
P21/c
P-1
Pbca
under vacuum
0.24
0.14
2×107
2×107
orange needle
orange plate
4.3845(2)
7.1311(4)
red needle
orange plate
orange plate
13.8023(2)
8.15218(10)
7.03233(10)
90
orange plate
32.967(9)
8.079(4)
6.986(3)
90
in air
0.26
0.29
0.15
0.15
three months
under vacuum
4.0461(3)
0.15
2×107
a (Å)
4.7328(5)
23.646(9)
8×106
under vacuum
in air
0.19
b (Å)
9.9861(7)
5.6266(10)
7.940(5)
three month
under vacuum
14.8584(10)
0.24
10.8786(16)
0.15
9×106
c (Å)
12.7965(6)
7.200(4)
1×103
in air
in air
under vacuum
0.20
81.629(13)
0.16
8×106
α(deg.)
90
90.248(2)
97.646(2)
98.184(2)
392.39(3)
1
90
0.039
0.069
SS-Bu
in air
0.022
0.015
14
43
69
37
52
4×103
β(deg.)
94.697(3)
80.329(12)
0.038
84.727(13)
0.018
90
102.402
90
90
three months
γ(deg.)
under vacuum
0.026
1×105
90
90
90
7×105
under vacuum
in air
0.014
0.025
0.019
4
V (Å3)
598.33(7)
281.86(8)
1351.9(12)
772.806(19)
2
1860.9(13)
4
three month
under vacuum
0.041
0.032
0.16
6×106
1×105
in air
Z-value
in air
2
1
under vacuum
0.11
-58
-63
-66
-61
-58
7
60
86
53
4×103
S(CN)2-Et
T (K)
150
150
298
298
271
298
1.337
2700
in air
0.18
0.15
3×101
D
(g cm−3)
1.79
1.602
1.711
1.564
1.489
catlchree months
under vacuum
0.073
1642
0.060
4×102
2×101
Total reflns.
under vacuum
1359
1789
1960
1414
in air
0.060
0.033
three month in
under vacuum
0.088
0.055
5×102
Unique reflns. (Rint)
1270
1703
1086
0.070
938
1306
1214
air
in air
0.028
6×101
R1 [F2 > 2σ(F2)]
0.0715
0.0187
0.0358
0.0439
0.0488
0.0505
under vacuum
0.14
0.06
0.11
2.4×106
1.9×105
8.8×105
1.8×105
3.4×106
7.0×105
1.9×106
6.2×104
3.0×106
6.4×104
SO-Et
OS-Me
OS-Et
OS-Pr
OS-Bu
wR2 [All
reflections]
GOF
in air
0.04
0.1575
0.0476
0.0948
0.1049
0.1284
0.1778
under vacuum
9.0×10−3
5.0×10−3
in air
6.0×10−3
4.0×10−3
128
72
101
56
1.348
1.071
12.3 (001)
31
1.001
1.003
1.071
13.3 (~ a)
19
1.012
16.1 (~ a/2)
18
under vacuum
8.3 (011)
0.15
0.09
XRD d (Å)
10.9 (~c)
11.8 (~ a/2)
in air
0.04
0.05
0.01
0.07
0.03
0.03
Tilt angle (°)
11, 21
27
18
under vacuum
0.04
in air
under vacuum
in air
0.007
0.04
0.02
68
51
82
that remarkable stability is observed using these thin-film
under ambient atmosphere for all the investigated devices (Table transistors.
2).
Apart from the thin-film transistors prepared with OS-Me and
SS-Me all the other transistors exhibit improved characteristics
compared to SS-Et thin-film transistors (Table 2).5 The collected
data clearly demonstrate that the best transistor performance is
observed in SO-Et, OS-Et, S(CN)2-Et and SS-Pr. Fig. 2(a) shows
transfer characteristics of an evaporated film SS-Pr transistor,
which shows electron mobility of 0.26 cm2 V-1 s-1 for the
measurement in air. Among the SS-R devices, SS-Pr seems to
be most suitable for thin-film transistors, showing the 0.1 cm2 V-
1 s-1 order mobility.
Since transistors of SS-Pr and SS-Bu show stability in air
even in the thin films, the long-term stability was investigated
(Fig. 2(a)). The transistor characteristics are practically
unchanged after three-month storage under vacuum (Table 2).
After further three-month storage in air, the mobility is
unchanged, though the threshold voltage increases to some
extent. At the same time, the on/off ratio decreases. However,
a close look to the transfer characteristics (Fig. 2(a)) reveals that
this is due to the increase of the off current, whereas the on
current does not change significantly. It should be emphasized
Figure 2. Transistor characteristics of an SS-Pr thin-film transistor: (a)
transfer characteristics measured under various conditions, and (b)
output characteristics measured in air. (c) Transfer characteristics of an
SS-Bu thin-film transistor.
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S(CN)2-Et exhibits high mobility (0.18 cm2 V-1 s-1) as well, thin-film transistors.21 SS-Me also shows tilted stacking
but the threshold voltage shows a comparatively large negative molecular arrangement with the interplanar distance of 3.497
Å
value, indicating the normally-on character (Fig. 3(a)). (a), but the succeeding layers are largely tilted alternately (Figs.
Normally-on transistors are sometimes observed in p-channel 4(c) and (d)). Short S-S contacts are found only in the interlayer
transistors using strong electron donors such as (c) direction. This seems disadvantageous to the charge transport.
tetrathiafulvalene (TTF),19 but electron-transporting normally-
Among OS-
R, only OS-Me has a tilted stacking ("-type)
on transistors are comparatively rare. This is due to the very structure of the SS-
R
type (Fig. 4(e)). The structure resembles
strong acceptor ability of S(CN)2-Et. In this case, after storage, SS-Pr, where all molecules are parallel to each other, and the
the increase of the off current is more important for the reduction interplanar distance along a is 3.419 Å. Short S-S contacts are
of the performance than the decrease of the on current.
found in the stacking (a) and interlayer (c) directions, but not in
SO-Et and OS-Et show similar transistor characteristics, but the side (b) direction.
the mobility measured in air is smaller than that under vacuum.
The threshold voltages show comparatively large positive
values, indicating the normally-off character. After several-week
storage in air, the mobility is not seriously affected, but the
threshold voltage increases considerably (Table
2 and
Supporting Information). The slight reduction of the air stability
could be related to the LUMO energy levels which are above -
4.0 eV. This is contrasting to the SS-R thin-film transistor series,
where the mobilities measured in air are similar to that under
vacuum, and the threshold voltage and the on/off ratios are not
significantly modified.
Figure 3. Transfer characteristics of a (a) S(CN)2-Et and (b) OS-Et thin-
film transistor measured under vacuum (blue) and in air (red).
Crystal structures
X-ray single-crystal structure analysis was carried out for SS-
Me
,
SS-Pr
,
OS-Me
,
OS-Et
,
OS-Pr, and OS-Bu. The crystal
have
data are listed in Table 3. Except for SS-Et,5 other SS-
R
Figure 4. Crystal structure of SS-Pr (a) viewed along the molecular long
axis, and (b) along the molecular short axis. Transfer integrals of the
LUMO–LUMO interactions are a = −19.2, b = −25.2, and p = 4.2 meV.
Short intermolecular S-S contacts are 3.641, 3.706, and 3.878 Å for a,
and 3.534 and 3.636 Å for p. Crystal structure of SS-Me (c) viewed
along the a axis, and (d) along the c axis. Transfer integrals of the
LUMO–LUMO interactions are a = −49.7, b = −0.9, p = −49.7, and q =
8.1 meV. Short S-S contacts are 3.597 Å for p, and 3.499 and 3.731 Å
for q. (e) Crystal structure of OS-Me. Transfer integrals of the LUMO–
LUMO interactions are a = −19.2 and b = −16.4 meV. Short S-S
contacts are 3.675 Å for a and 3.683 Å along the c - a axis.
similar tilted stacking structures (Fig. 4). SS-Pr is isostructural
to SS-Bu; the molecules are located on inversion centers, and all
molecules are parallel to each other (Fig. 4(a) and (b)). The
interplanar distance along a is 3.508 Å. This structure is close to
the "-type structure known in bis(ethyleneditho)
tetrathiafulvalene (BEDT-TTF) salts.20 This contrasts with SS-
Et, where the long axes of the stacking molecules are alternately
twisted.5,10 SS-Et has many short intermolecular S-S contacts
along the three different crystal axes to make a three-dimensional
network.5 In contrast, SS-Pr has short S-S contacts in the
conducting (ab) layer, but no short contacts in the interlayer (c)
direction (Fig. 4 caption). Since the transfer integrals along the
a and b axes are comparable, two-dimensional electron transport
is expected. SS-Et has three-dimensional tight packing, which
is advantageous to single-crystal transistors, whereas SS-Pr has
a more usual layer structure, which seems more suitable for the
All other OS-R compounds have herringbone structures (Fig.
5(a)). The crystals are not strictly isostructural; OS-Et and OS-
Bu belong to the same space group, but OS-Pr has a different
space group. The formers are isostructural to SO-Et 10
In the
.
former crystals, the a axis contains two alternately tilted
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molecular layers (Fig. 5(b)), while OS-Pr contains a single
parallel layer (Fig. 5(c)). This seems to depend on the even/odd
carbon number of the alkyl chains. A limited number of short S-
S contacts exist only along the stacking (c) axis. The existence
of many S-S contacts has been suggested as the origin of the
tilted stacking structure in SS-R 5
.
In OS-R, the weakened
intermolecular interaction seems to result in the ordinary
herringbone packing. The slight reduction of the air stability is
not only attributed to the acceptor ability but also to the reduced
S-S interactions.
The dihedral angles of OS-Et (63.9°) and SO-Et (65.8°) are
smaller than those of OS-Pr (70.9°) and OS-Bu (68.7°). It has
been known that the transfer integrals increase with decreasing
the dihedral angle.22 This is in agreement with larger mobilities
of the former compounds than the latter compounds. It is
noteworthy that OS-Bu is isostructural to OS-Et, and the
comparatively large dihedral angle comes from the alkyl chain
length. From this, we suppose that further elongation of the alkyl
chain length will not increase the transistor performance.
Figure 6. X-ray diffraction patterns of (a) SS-
Et, and (b) SO-Et and OS- . Atomic force microscopy (AFM) images
of (c) SS-Pr, (d) SS-Bu, (e) OS-Me, (f) OS-Et, (g) OS-Pr, and (h) OS-
Bu
R together with S(CN)2-
R
.
Correlation between crystal structure and transistor
performance
Figure 5. (a) Crystal structure of OS-Pr viewed along the molecular
long axis. Short S-S contacts are 3.675 (OS-Me), 3.695, 3.874 (OS-Et),
3.796 (OS-Pr), 3.745 Å (OS-Bu) all along the stacking (c) axes.
In general, the SS-
stacking structure, and SO-
structure. Both attain good transistor performance.
R
compounds show the tilted ("-like)
and OS- have the herringbone
R
R
Interlayer structures of (b) OS-Et and (c) OS-Pr
.
SS-Et is exceptional due to the the twisted (nonparallel)
stacking structure. This characteristic crystal structure may be
associated with the low performance of the thin-film transistors
in comparison with the single-crystal transistors. SS-Pr has a
more usual layered structure, and attains excellent performance
in the thin-film transistors.
SS-Et has many three-dimensional intermolecular S-S
contacts, which are related to the excellent air stability of the
transistors. In general, with increasing the alkyl chain length, the
number of S-S interactions decreases, and the air stability
decreases gradually. In the herringbone structures, the molecular
tilt angle increases with increasing the alkyl chain length, to
reduce the transistor performance. Accordingly, the transistor
performance and the air stability are maximized around the Et
and Pr compounds. The intermolecular S-S contacts are less
Thin film characterizations
Thin films of these compounds show sharp X-ray diffraction
(XRD) peaks (Fig. 6(a)). The extracted d values (Table 3) are in
good agreement with the largest lattice constants. Therefore, the
molecules are standing perpendicular to the substrates. The tilt
angles of the molecular long axis from the substrate normal are
estimated from the crystal structure (Table 3). The molecules in
the stacking structures (SS-
the herringbone structures (< 20o).
R) are more largely tilted (~
30o) than
Atomic force microscopy (AFM) images show densely
packed microcrystals. The good performance of these materials
is most probably related to the good crystallinity. Only OS-Me
shows comparatively loose packing, and this may be responsible
for the exceptionally low mobility, although the crystal structure
pronounced in OS-
levels, this is related to the slightly reduced air stability of the
OS- transistors.
R. Together with the slightly higher LUMO
R
Crystal structures of SS-Me and OS-Me are exceptional;
owing to the largely tilted stacking structures, these compounds
show much reduced transistor performance.
has a close resemblance to SS-Pr
.
S(CN)2-Et has a stacking structure,11 but the molecules are
largely displaced both along the molecular short and long axes.
There are several intermolecular S-S contacts. The good
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transistor performance and the moderate air stability are
consistent with this crystal structure.
1
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Conclusions
We have performed a systematic study on a series of thin-
film transistors based on birhodanines, OS-
and Bu), and their sulfur analogues SS- . These compounds
exhibit excellent n-channel transistor characteristics with long-
term air stability. A combination of X-ray crystal structure
studies and thin-film characterization (AFM and XRD) reveals
the influence of the sulfur atoms on the molecular packing and
R (R = Me, Et, Pr,
R
the performance of the transistors. The SS-
characteristic tilted stacking structures attributed to the
pronounced intermolecular S-S interactions, but the OS-
crystals have the ordinary herringbone structure owing to the
reduced intermolecular interactions. The SS- thin-film
transistors exhibit better performance than the OS- transistors.
In the SS- series, the elongation of the alkyl chain length from
R crystals show
2
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R
methyl to propyl improves the solubility while it still maintains
good crystallinity with a small decrease of the intermolecular S-
S interactions, leading altogether to the improvement of the
transistor characteristics.
remarkable stability even after air exposure for three months.
In particular, SS-Pr exhibits
4
Acknowledgements
This work was partly supported by ACT-C Grant Number
JPMJCR12ZB from JST, Japan, and a Grant-in Aid for Scientific
Research (B) (No. 16K13974) from the Ministry of Education,
Culture, Sports, Science, and Technology of Japan. We thank
the Agence Nationale de la Recherche, France (ANR project
n°12-BS07-0032) for financial support. The authors are grateful
to Tokyo Institute of Technology Center for Advanced Materials
Analysis for XRD measurement and Prof. Kakimoto for AFM
measurements.
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Department of Materials Science and Engineering, Tokyo Institute of
Technology, O-okayama 2-12-1, Meguro-ku, 152-8552, Japan. E-mail:
iijima.k.ae@m.titech.ac.jp; mori.t.ae@m.titech.ac.jp
b Institut des Sciences Chimiques de Rennes, Université de Rennes 1,
CNRS UMR 6226, Matière Condensée et Systèmes Electroactifs
(MaCSE), campus de Beaulieu, Bât 10A, 35042 Rennes cedex, France.
c Present address: National Institute of Advanced Industrial Science and
Technology (AIST), Tsukuba 305-8565, Japan
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*E-mail: mori.t.ae@m.titech.ac.jp
†
Electronic supporting information (ESI) available: CCDC 1558710,
1558711, 1558718, 1558720, 1558721, and 1558724 contain the
supplementary crystallographic information. Additional information for
preparative details, molecular orbitals, devices fabrication, transistor
characteristics, crystal structures, and thin film properties.
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The table of contents entry
Title
Birhodanines and their sulfur analogues for air-stable n-channel organic transistors
Text (one sentence, of maximum 20 words, highlighting the novelty of the work)
Birhodanines and the sulfur analogues are excellent n-channel transistor materials with long-term
air stability even in the evaporated films.
Keywords
organic transistors, organic semiconductors, n-channel characteristics, rhodanine
Authors
Kodai Iijima, Yann Le Gal, Toshiki Higashino, Dominique Lorcy, and Takehiko Mori
ToC figure (maximum size 8 cm x 4 cm)