Phenyl substitution in tetracene: a promising strategy to boost charge mobility in thin film transistors

Article abstract of DOI:10.1039/c6tc04624j

Tetracene, one of the polyacene derivatives, shows eminent optical and electronic properties with relatively high stability. To take advantage of the intrinsic properties of the tetracene molecule and explore new semiconductors, herein, we report the design and synthesis of two novel p-channel tetracene derivatives, 2-(4-dodecyl-phenyl)-tetracene (C12-Ph-TET) and 2-phenyl-tetracene (Ph-TET). Top contact OTFTs were fabricated using these two materials as semiconductor layers, with charge mobilities up to 1.80 cm² V^?1 s^?1 and 1.08 cm² V^?1 s^?1, respectively. Our molecular modeling results indicate that the introduction of phenyl into tetracene can improve the efficient charge transport in electronic devices as a result of the increased electronic coupling between the two neighboring planes of the molecules. AFM images of the thermally evaporated thin films of these two materials show large grains, which correspond to the high mobilities of these devices. Consequently, the mobility of our OTFTs based on C12-Ph-TET is the highest for OTFTs based on tetracene derivatives reported to date. The single crystal analyses show the existence of π-π stacking interactions within the molecules with the introduction of mono-phenyl substituents, which is the main cause of the increased mobility. The impressive properties of these two materials indicate that the introduction of alkyl-phenyl and phenyl group could be an excellent method to improve the properties of the organic semiconductor materials.

Full text of DOI:10.1039/c6tc04624j

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ISSN 2050-7526
PAPER
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Nguyên T. K. Thanh, Xiaodi Su et al.
Fine-tuning of gold nanorod dimensions and plasmonic properties using
the Hofmeister effects
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Phenyl Substitution in Tetracene: A Promising Strategy to Boost
Charge Mobility in Thin Film Transistors
Wenjun Xu,a Yaowu He,a Imran Murtaza,b,c Dongwei Zhang,a Aiyuan Li,a Zhao Hu,a Xingwei Zeng,a
Yitong Guo,a Yanan Zhu,a Ming Liu, a Hong Meng*,a,b
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
Tetracene, one of the polyacene derivatives, shows eminent optical and electronic properties with relatively high stability.
To take advantage of the intrinsic properties of tetracene molecule and explore new semiconductors, we report here the
design and synthesis of two novel p-channel tetracene derivatives, 2-(4-dodecyl-phenyl)-tetracene (C12-Ph-TET) and 2-
phenyl-tetracene (Ph-TET). Top contact OTFTs were fabricated using these two materials as semiconductor layers, with
charge mobilities up to 1.80 cm2 V-1 s-1 and 1.08 cm2 V-1 s-1, respectively. Our molecular modeling results indicate that the
introduction of phenyl into tetracene can improve the efficient charge transport in electronic devices as a result of the
increased electronic coupling between two neighboring planes of the molecules. AFM images of the thermally evaporated
thin films of these two materials present large grains, which correspond to the high mobilities of these devices.
Consequently, the mobility of our OTFTs based on C12-Ph-TET is the highest amid OTFTs based on tetracene derivatives
reported up till now. The single crystal analyses show the existance of π-π stacking interactions within the molecules, by
the introduction of mono-phenyl substituents, which is the main cause of increased mobility. The impressive properties of
these two materials indicate that the introduction of alkyl-phenyl and phenyl could be an excellent method to perk up the
properties of organic semiconductor materials.
www.rsc.org/
with pentacene and anthracene due to its significantly lower
rate of decomposition and larger π-conjugation system.19
Mobility of the OTFTs based on tetracene thin films has
reached up to 0.12 cm2 V-1 s-1,20 and its single crystal OTFTs
1. Introduction
With the scientific and technological development, organic
thin-film transistors (OTFTs) have enticed the industry to their
potential applications in organic electronic products such as
active matrix organic light-emitting diodes, organic sensors,
radio-frequency identification tags and many others.1-4
Different structures of organic semiconductors have been
developed in the recent years, such as organic semiconductors
based on anthracene,5-9 and pentacene10-13 derivatives,
benzothieno[3,2-b]benzothiophene (BTBT) core based
structures14-18 and so on. Polyacene derivatives such as
tetracene, pentacene and anthracene have been widely
investigated as semiconductor materials for organic thin film
transistors. However, tetracene provides a better tradeoff
between stability and charge transfer properties compared
have achieved 2.4 cm2 V-1 s-1.21 Due to its high external
quantum efficiency, the single crystal of tetracene has also
been used in the fabrication of organic light-emitting field-
effect transistors.22, 23 Rubrene, one of the most admirable
tetracene derivatives, has shown good performance as single
crystal semiconductor in OTFTs24 and has been used in the
light-emitting organic field effect transistors as well, due to its
remarkable optoelectronic properties.23 In addition, rubrene
has shown a very high intrinsic mobility of 40 cm2 V-1 s-1,25
divulging the absolute potential of fabricating high mobility
OTFTs based on tetracene derivatives.
Though the single crystal OTFTs based on tetracene have
shown higher mobility than amorphous silicon TFTs and the
rubrene single-crystal has shown very high intrinsic mobility,
the defect-free single crystals are not easy to fabricate. As a
result, OTFTs based on single crystal tetracene are not
practical for large-scale applications. Moreover, mobility of
OTFTs based on tetracene fabricated by thermal evaporation is
not high enough. The highest mobility obtained in normal self-
assembled monolayers (SAMs) modified OTFTs based on
different tetracene derivatives is 0.5 cm2 V-1 s-1 (Table S1),26-33
which were fabricated by Jeffrey A. Merlo32 et al.
For tuning properties and improving performance of organic
semiconductors, expansion of π-conjugation and introduction
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of alkyl chain are two vital methods, which are further proved The absorption peaks at the wavelengths of 451, 483 and 536
by the examples of BTBT derivatives.14, 34, 35 A series of reports nm, in the thin film state, may be ascribed to the π-π*
demonstrate that the introduction of long alkyl substituent transition of localized tetracene core and the phenyl
groups leads to higher mobility of OTFTs based on BTBT substituent. The bathochromic shift and the increase in the
derivatives.14, 34, 35 Morphology of the thin films, one of the ratio of the vibronic peak intensities between the 0-0 and 0-1
most important contributing factors to the stability and peaks of the absorption spectra in the thin film state as
repeatability of the OTFTs, has stringent correlation with compared with that in the solution state, are the two strong
molecular planarity, which has been established by a series of evidences to deduce the J-aggregation in the thin films.40 By
experiments.36, 37
comparing the absorption peaks of the C12-Ph-TET and Ph-TET
In this context, to maintain the advantages and improve the thin films, we can make a conclusion that the introduction of
performance of tetracene, we introduce 4-dodecyl-phenyl and the long dodecyl chain does not have profound influence on
phenyl group into the tetracene molecule as substituents and the UV absorption of the thin films. This result is different from
report an efficacious synthesis of 2-(4-dodecyl-phenyl)- the published experiments34 and it shows that the introduction
tetracene (C12-Ph-TET) and 2-phenyl-tetracene (Ph-TET) as of the long alkyl chain makes trivial contribution to disturb the
new kinds of OTFT semiconductor materials. C12-Ph-TET and aggregation of the aromatic part of the molecule.
Ph-TET were synthesized by Suzuki coupling as shown in
Scheme 1. OTFT devices were fabricated using these two
materials as active layers, showing the highest charge The normalized UV-Vis absorption spectra indicate the optical
mobilities up to 1.80 cm2 V-1 s-1 and 1.08 cm2 V-1 s-1, bandgap of the materials, which can be calculated from the
respectively. To the best of our knowledge, the mobility of absorption onset wavelength. The calculated result of the
OTFTs based on C12-Ph-TET is the highest value amid OTFTs optical bandgap (Eopt) is 2.21 eV for both the materials. Figure
based on tetracene derivatives reported up till now. The 1b shows the cyclic voltammograms of the C12-Ph-TET and Ph-
properties of these two materials clearly demonstrate that the TET thin films. The first oxidation peak values of C12-Ph-TET
introduction of 4-dodecyl-phenyl and phenyl could be a and Ph-TET, used in the calculation of HOMO level, appear at
virtuous method to improve the properties of organic 0.74 and 0.64 V respectively, using ferrocene as inner standard.
semiconductor materials. This conclusion is also supported by The calculated values for C12-Ph-TET and Ph-TET are: EHOMO= -
our computational modeling results presented in the next 5.46 eV and -5.36 eV, ELUMO= -3.25 eV and -3.15 eV,
section.
respectively. In the literature, both HOMO and LUMO levels
have been calculated from cyclic voltammograms.41 However,
we could not directly obtain the LUMO energy level from cyclic
voltammograms, as there are no reductive peaks in the graphs.
LUMO levels were calculated by using the equation: ELUMO
=
EHOMO + Eopt).42-44 The electronic properties of C12-Ph-TET and
Ph-TET are summarized in Table 1.
Scheme 1. Synthesis of C12-Ph-TET and Ph-TET.
2. Results and Discussion
2a. Synthesis
The 2-bromo-tetracene was synthesized according to
patent38
a
delivered
and
2-(4-dodecyl-phenyl)-4,4,5,5-
tetramethyl-[1,3,2]-dioxaborolane was synthesized according
to the literature.39 The C12-Ph-TET and Ph-TET were both
synthesized by Pd-mediated Suzuki coupling, allowing the
reaction at 100 °C under vigorous stirring for 2 days. Details of
synthetic routes are reported in the supporting information.
Fig. 1 (a) Normalized UV-Vis absorption spectra of C12-Ph-TET
and Ph-TET in the thin film and solution states. (b) Cyclic
voltammetry (CV) graphs of C12-Ph-TET and Ph-TET. The
oxidation potential is obtained at the onset of the cyclic
voltammogram.
2b. Optical and Electrochemical Properties
The C12-Ph-TET and Ph-TET show nearly the same absorption
peaks in both the thin film and solution states (Figure 1a). The
manifestation of this phenomenon could be due to the same
π-conjugation system of these two compounds. The onset of
UV absorption of both the thin films occurs at the wavelength
of 562 nm and the maximum absorption peaks appear at the
wavelength of 536 nm. However, in the solution state of both
the materials, the absorption onset appears at the wavelength
of 500 nm. The UV data reveal the fact that the substitution of
long alkyl chain has little influence on the UV absorption peaks.
Table 1. Electronic properties of C12-Ph-TET and Ph-TET.
Compound
λedge/nma Eg/eVb
EHOMO/eVc ELUMO/eVd
C12-Ph-TET 562
2.21
-5.46 -3.25
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single crystal XRD data, however, the quality of the single
crystals was not good enough to fabricate single crystal OTFTs.
Ph-TET
562
2.21
-5.36
-3.15
2d. Morphological Characterization.
aFrom ultraviolet absorption spectra of these two compounds
(thin film). bCalculated by λedge/nm of ultraviolet absorption
X-ray diffraction (XRD) data and atomic force microscope (AFM)
images were obtained to reveal the morphology of the thin
films deposited by thermal evaporation on the n-
octyltrichlorosilane (OTS)-treated Si/SiO2 substrate. Thin films
of C12-Ph-TET were deposited on the substrates at room
spectrum(thin film) using the equation: 1240/λonset
cyclic voltammetry data vs. Fc/Fc+ of these two compounds
.
cFrom
+
using equation HOMO = -[Eox - E(Fc/Fc + 4.8 ](eV). Calculated
d
)
by Eg and EHOMO using equation ELUMO = (EHOMO + Eopt) (eV).42-44
temperature, 60
TET were deposited at room temperature and 60
efforts to deposit Ph-TET at 100 C were unsuccessful. The XRD
results show that the thin films of Ph-TET fabricated at 60
°C and 100
°
C, whereas the thin films of Ph-
°
C because
2c. Crystal Structure
°
In order to correlate transport properties with the packing
structure of molecules in the condensed phase, we performed
single crystal X-ray analysis. Notwithstanding various futile
methods, we successfully attained single crystals of Ph-TET by
°C
are far more crystallized than the thin films fabricated at room
temperature, as there are higher incisive peaks in the XRD data.
This result reveals that Ph-TET has excellent oriented-growth
physical vapor transport. Depicted in Figure
2 are the
property. The incisive peak at 2θ = 5.5
°can be assigned to the
molecular and packing structures of Ph-TET demonstrating
that the single crystal of Ph-TET is monoclinic crystal belonging
to the P21 space group with crystal parameters of a = 6.1567(7)
Å, b = 7.2515(8) Å and c = 16.757(2) Å, whereas the crystal
structure of tetracene is triclinic (Figure S1). The distance
between the two H-atoms of the Phenyl and neighboring
tetracene molecules is about 2.606 Å (Figure 2a) and the
distance between the two H-atoms of neighboring teracene
cores is 2.754 Å (Figure S1a). The shorter the distance between
the two neighboring atoms, the more is the enhancement of
the overlay electronic coupling, which favors the charge
transport. To make a deeper understanding of the phenyl
substitution on the semiconductor properties, the charge
transfer integrals were calculated by using the software
Amsterdam Density Functional (ADF). The software uses a
generalized gradient approximation with the PW91 functional
and the basis set of triple-Z 2 plus polarization function (GGA:
PW91/TZ2P) for modeling the charge transfer properties by
utilizing the single crystal structure of the organic
semiconductor materials. The charge transfer integrals of Ph-
TET were calculated for the adjacent molecules along their π-π
stacking direction, which resulted in a charge transfer integral
of about 87.52 meV (Figure 2d), which is much higher than
that of the tetracene (70.15 meV, Figure S1d). This theoretical
result predicts that the phenyl substitution has positive
influence on the improvement of the hole mobility of
tetracene and is supplemented by our experimental results as
well. Moreover, we found that the dihedral angle between two
tetracene planes is 51.38o (Figure S1c) and that between two
tetracene planes of Ph-TET is 46.59o (Figure 2c), which is
another contributing factor towards increased mobility as we
know that smaller the angle between the two neighboring
planes of the molecule, the more is the overlap of the
electronic coupling and hence higher the mobility. The packing
structures of Ph-TET are also shown in Figure 2, portraying the
(0 0 1) reflection and a d-spacing of 15.82 Å can be calculated
by using Bragg’s equation, which is comparable to the value
Fig. 2 Molecular structure, shortest intermolecular distance
between two H-atoms and torsion angle between tetracene
and phenyl planes (a), packing pattern and molecular length of
Ph-TET projected along the crystallographic a-axis (b), c-axis
projection showing the herringbone structure and dihedral
angle between two tetracene planes of Ph-TET (c), charge
transfer integrals in the single crystal of Ph-TET molecules (d).
mean angle of 46.59°between the tetracene planes and the
molecular arrangement pattern of Ph-TET as
a
typical
herringbone motif (Figure 2c). The interlayer spacing (d-
spacing) between the tetracene planes calculated by the single
crystal XRD data is 16.757 Å. We were lucky to obtain the
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big grain size makes enormous contribution to higher
calculated by single crystal XRD. Four reflection peaks mobility.36, 37 The same conclusion could be drawn to elucidate
appearing at 5.47, 10.74, 16.01, 21.33 can be assigned to (0 0 the data we obtained for the thin films of Ph-TET. Ph-TET thin
1), (0 0 2), (0 0 3) and (0 0 4) based on the single crystal XRD films fabricated on the substrate at both the room
data of Ph-TET. From the single crystal and thin film XRD d- temperature (Figure 4d) and 60
°C (Figure 4e) show big
spacing results, we can conclude that the Ph-TET has an edge- crystalline size, which increases with the substrate
on orientation to the substrate surface. However, the XRD temperature. We can also make a conclusion that for the long
data of C12-Ph-TET are rather diverse. The XRD data of the alkyl chain compound C12-Ph-TET, high substrate temperature
C12-Ph-TET thin films fabricated at 100
peaks at 3.0 than the thin films fabricated at room not change much the molecular orientation.
temperature and 60 C, which show higher crystallization of The molecular length of Ph-TET is 15.711 Å (Figure 2b), which
the thin films fabricated at 100 C (Figure 3). Meanwhile, a is calculated by the single crystal XRD data. Comparing the
new peak at 4.4 appears, as the substrate temperature rises molecular length with the AFM step value, which is around 16
to 100
°C show higher incisive has a beneficial influence on the growth of grain size and does
°
°
°
°
°
C, which also reveals a better crystallinity in the thin Å (Figure S4), it can be deduced that the compound Ph-TET
films and perhaps it reveals the formation of a new phase.45
adopts a layer-by-layer configuration on the wafers. By making
a comparison between these two materials, we can deduce
that the long alkyl chain increases the grain size of the thin
films more effectively when the substrate temperature is high
enough. This phenomenon could be explained by the
molecular arrangement effect of the long alkyl chain.
2e. OTFT Properties
The bottom-gate top-contact OTFT devices were fabricated by
thermal evaporation and evaluated under ambient conditions.
OTFTs based on C12-Ph-TET and Ph-TET show typical p-type
transfer and output characteristics as shown in Figure 5. It can
be seen in Table 2 that mobilities of the devices based on both
C12-Ph-TET and Ph-TET are higher than the thin film OTFTs
based on tetracene19, 46-48 and the mobility results supplement
our XRD and AFM data very well. Average mobility of ten
devices based on C12-Ph-TET is 1.63 cm2 V-1 s-1, with the
highest value obtained is 1.80 cm2 V-1 s-1. Whereas, ten devices
based on Ph-TET accomplished the average mobility of 0.69
cm2 V-1 s-1, and the highest value of 1.08 cm2 V-1 s-1. As shown
in Table 2, we can easily find that the mobility of phenyl-
dodecyl substituent tetracene derivative is extremely
responsive to the substrate temperature. This result reveals
the fact that the properties of the OTFTs based on long alkyl
derivatives can be controlled by altering the substrate
temperature. This remarkable performance makes C12-Ph-TET
as one of the best tetracene derivatives. Moreover, our OFETs
show high threshold voltages which may be due to the facts
that firstly the HOMO level of C12-Ph-TET (-5.46 eV) and Ph-
TET (-5.36 eV) doesn’t match well with the work function of
gold (-5.1 eV) and secondly the charge trap states limit the
charge injection. In order to check the operational stability of
the OTFT devices, we obtained transfer characteristics for 100
sweep cycles in the ambient conditions, and the data showed
Fig. 3 XRD data of C12-Ph-TET (a) and Ph-TET (b) thin films
fabricated by thermal evaporation.
The results demonstrate that there is obvious molecular
orientation in the thin films, which is also portrayed by the
AFM images. To further probe the morphology of C12-Ph-TET
and Ph-TET thin films fabricated by thermal evaporation at
different substrate temperatures, atomic force microscope
(AFM) was utilized. The AFM images shown in Figure 4 depict
that thin films of the two synthesized compounds have totally
different morphologies. For C12-Ph-TET, the thin films
fabricated on the substrate at room temperature (Figure 4a)
show no big grains, while those fabricated on the substrate at
60
°C show small grains (Figure 4b). However, the thin films
fabricated at 100
°
4c). The AFM results are also consistent with the mobility
C show big grains in the AFM images (Figure
values, as it has been proved by a series of experiments that
no
obvious
changes
(Figure
S7).
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Table 2. OTFT properties of C12-Ph-TET and Ph-TET.
b
Compound
C12-Ph-TET
Tsub
rt
/°C
μOTFT/cm2/Vsa
Ion/Ioff
VT/Vc
0.11 (0.08 ± 0.02)
0.33 (0.22 ± 0.07)
1.80 (1.63 ± 0.11)
0.45 (0.33 ± 0.11)
0.52 (0.35 ± 0.09)
1.08 (0.69 ± 0.20)
(8.27 ± 7.02) × 104
(9.57 ± 5.13) × 105
(6.80 ± 3.71) × 106
(3.15 ± 2.81) × 105
(1.00 ± 0.36) × 107
(1.71 ± 0.58) × 106
-7.7 ± 1.8
60
-15.2 ± 1.8
-18.7 ± 2.5
-12.2 ± 2.2
-16.6 ± 2.2
-21.2 ± 2.5
100
120
rt
Ph-TET
60
aValues without brackets are the highest mobilities of the devices and values within brackets are average values of 10 devices.
bAverage on/off ratio value of 10 devices. cAverage threshold voltage value of 10 devices.
Fig. 4 AFM images of C12-Ph-TET and Ph-TET thin films fabricated by thermal evaporation. (a) C12-Ph-TET, substrate: room
temperature; (b) C12-Ph-TET, substrate: 60
Ph-TET, substrate: 60 C.
°C; (c) C12-Ph-TET, substrate: 100 °C; (d) Ph-TET, substrate: room temperature; (e)
°
Fig. 5 Transfer curves of (a) C12-Ph-TET,substrate:room temperature; (b) C12-Ph-TET, substrate:60
100 C; (d) Ph-TET, substrate: room temperature; (e) Ph-TET, substrate: 60 C and output curves of (f) C12-Ph-TET, substrate:
room temperature; (g) C12-Ph-TET,substrate: 60 C; (h) C12-Ph-TET, substrate: 100
(j) Ph-TET, substrate: 60 C.
°C; (c) C12-Ph-TET, substrate:
°
°
°
°C; (i) Ph-TET, substrate: room temperature;
°
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triphenylphosphinepalladium (0.09 g, 0.081 mmol) , toluene
(40 mL) and 2 mol/L K2CO3 (12.15 mL)were added. After
nitrogen-blowing for 20 min, the reacting system was stirred
3. Conclusions
In conclusion, we discovered two new phenyl-tetracene
derivatives, 2-(4-dodecyl-phenyl)-tetracene and 2-phenyl-
tetracene and studied their optical and electrochemical
properties. OTFTs based on these two materials were
fabricated, which presented the highest charge mobilities up
to 1.80 cm2 V-1 s-1 and 1.08 cm2 V-1 s-1, respectively. These two
values are higher than the other reported tetracene
derivatives. We also systematically analyzed the structural and
morphological data of the thin films fabricated from these two
materials and found that the mobilities of the devices
remarkably supplement the morphology of the thin films. It is
observed that the two substituent groups dramatically
enhance the charge carrier mobility of tetracene. The single
crystal analyses provide a simple means of understanding
crystal effects and show that regardless of the twisting caused
by the phenyl substituent, π-π stacking interactions take place
within the molecules that are in accord with the increase in
mobility. By utilizing the single crystal data, we calculated
charge transfer integrals of Ph-TET and tetracene, which
clearly demonstrate that the introduction of phenyl into
tetracene can improve the efficient charge transport in
electronic devices as a result of the increased electronic
coupling between two neighboring planes of the molecules
and consequently has positive influence on the hole mobility.
These results show that the introduction of phenyl and long
alkyl chain is an exceptional method to fine tune the
properties of organic semiconductor materials and has
profound influence on the morphology and grain size of the
organic semiconductor thin films, which leads to an improved
performance of the device. The obtained high mobility phenyl
substituted tetracene semiconductors not only provide a new
way to improve the device performance but also append one
of the highest organic semiconductor families beyond the
recent BTBT derivative tribes.
and heated to 100
°C for 48 h. After cooling to room
temperature, the sediments were separated by filtration and
washed twice with toluene. The crude product was purified by
sublimation in a 5-zone furnace to give an orange product
(2.71 g, 70.6%).
1
C12-Ph-TET: H NMR (CDCl3, 300 MHz): δ 8.71 (s, 1H), 8.67 (s,
3H), 8.19 (s, 1H), 8.09-7.99 (m, 3H), 7.73-7.70 (m, 3H), 7.42-
7.38 (m, 2H), 7.33 (d, 2H, J = 8.0 Hz), 2.69 (m, 2H),1.69 (m, 2H,
CH2) 1.27 (m, 18H, 9×CH2), 0.88 (t, 3H, J = 6.6 Hz). HRMS (APCI),
m/z calculated for C36H41[M+H]+: 473.3208. Found: 473.3204.
Structure of the C12-Ph-TET was confirmed by NMR (Bruker,
300MHz) and high resolution mass spectrum (HRMS).
We could not obtain the 13C NMR data of C12-Ph-TET due to its
low solubility.
Synthesis of 2-phenyl-tetracene
To a 350ml pressure bottle, 2-Bromotetracene (2.5 g, 8.1
mmol), phenyl-4,4,5,5-tetramethyl-[1,3,2]-dioxaborolane (2.49
g, 12.2 mmol), methyltrioctylammoniumchloride (1.64 g, 4.05
mmol), tetrakis triphenylphosphinepalladium (0.09 g, 0.081
mmol), toluene (40 mL) and 2 mol/L K2CO3 (12.15 mL) were
added. After nitrogen-blowing for 20 min, the reacting system
was stirred and heated to 100 °C for 48 h. After cooling to
room temperature, the sediments were separated by filtration
and washed twice with toluene. The crude product was
purified by sublimation in a 5-zone furnace to give an orange
product (1.33 g, 53.6%).
1
Ph-TET: H NMR (CDCl3, 300 MHz): δ 8.75 (s, 1H), 8.70 (s, 3H),
8.23 (s, 1H), 8.12 (d, 1H, J = 9.2 Hz), 8.05-8.02 (m, 2H), 7.84-
7.80 (m, 2H, J = 7.1 Hz), 7.75-7.72 (m, 1H), 7.55 (t, 2H, J = 7.5
Hz), 7.46-7.41 (m, 3H). HRMS (APCI), m/z calculated for
C24H17[M+H]+: 305.1330. Found: 305.1333.
Structure of the Ph-TET was confirmed by NMR and HRMS.
We could not obtain the 13C NMR data of Ph-TET due to its low
solubility.
4b. General procedures and experimental details.
4. Experimental Section
4a. Synthesis and characterization
Cyclic voltammetry
The organic semiconductor materials C12-Ph-TET and Ph-TET
were synthesized by Suzuki Coupling.
The C12-Ph-TET and Ph-TET thin films on the platinum
electrode were deposited by thermal evaporation. To detect
HOMO and LUMO of the two compounds, 0.1 mol L-1
Synthesis of 2-(4-dodecyl-phenyl)-tetracene
tetrabutylammoniumhexafluorophosphate
(Bu4NPF6)
of
To a 350 ml pressure bottle, 2-bromotetracene (2.5 g, 8.1
mmol),2-(4-Dodecyl-phenyl)-4,4,5,5-tetramethyl-[1,3,2]-
anhydrous acetonitrile (CH3CN) solution was made. After
piping Nitrogen in the solution for 30 min and keeping the
solution in Nitrogen atmosphere, the CV data was obtained at
dioxaborolane(4.55
g,
12.2
mmol),
methyltrioctylammoniumchloride (1.64 g, 4.05 mmol), tetrakis
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a scan rate of 100 mV s−1, using Ag/Ag+ as the reference constant support during the development of this article. CCDC
electrode (+0.08 V vs Ag/Ag+ nonaqueous reference electrode). 1481132 contains the supplementary crystallographic data for
The Ag/Ag+ electrode was made by soaking a clean Ag wire this paper.
into 0.01 mol L-1 AgNO3 solution in dry CH3CN and 0.1 mol L-1
tetrabutylammoniumhexafluorophosphate (Bu4NPF6).
Notes and references
OTFT devices fabrication
‡Footnotes relating to the main text should appear here. These
might include comments relevant to but not central to the
matter under discussion, limited experimental and spectral data,
and crystallographic data.
The bottom-gate top-contact OTFT devices were fabricated on
the OTS treated n-Si wafers with approximately 200 nm of SiO2
layer. In this case, the Si wafers were cleaned by acetone,
deionized water and isopropanol at room temperature in the
ultrasonic bath for 20 min. After ultrasonic cleaning, the n-
doped Si wafers were exposed to the ultraviolet radiation for
20 min. Then the wafers were immersed in the 0.1 mol L-1
1
2
3
4
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6
, 10032.
6
7
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are 400ꢀm / 40
1000 m / 100
ꢀ
m, 600
ꢀm / 60 ꢀm, 800 ꢀm / 80 ꢀm, and
ꢀ
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：
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This work was financially supported by Shenzhen Key
Laboratory of Organic Optoelectromagnetic Functional
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(ZDSYS20140509094114164), the Shenzhen Peacock Program
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Nanshan Innovation Agency Grant (No. KC2015ZDYF0016A),
Guangdong Key Research Project (Nos. 2014B090914003,
2015B090914002), Guangdong Talents Project, National Basic
Research Program of China (973 Program, No. 2015CB856505),
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