Paper
Journal of Materials Chemistry C
and drop-coated at 3000 rpm for 40 s on the cleaned ITO elec- water and the mixture was extracted with dichloromethane. The
ꢁ
trode. Subsequently, the PEDOT:PSS lm was baked at 150 C combined organic phases were dried over magnesium sulfate.
for 15 min in air to give a thin lm. A blend of the polymer and Aer the solvents were evaporated under vacuum, the crude
phenyl butyric acid methyl ester (PCBM) (different weight product was puried on a silica gel column with petroleum
ꢀ1
ratios, 10 mg mL for polymer) was dissolved in o-dichloro- ether–ethyl acetate (1 : 2, v/v) as eluent, to give compound 2 as
benzene (ODCB), and spin-cast at 1700 rpm for 90 s onto the an orange-red oil (29.18 g, 78% yield).
1
PEDOT:PSS layer. A bilayer cathode consisting of Ca (ꢂ20 nm)
H-NMR (CDCl
3
, 400 MHz): d: 7.70 (dd, J ¼ 0.9, 1.5 Hz, 1H),
capped with Al (ꢂ40 nm) was thermally evaporated under a 7.41 (dd, J ¼ 1.5, 1.8 Hz, 1H), 6.59 (dd, J ¼ 0.9, 1.8 Hz, 1H), 3.48
ꢀ5
shadow mask with a base pressure of ca. 10 Pa. The active area (q, J ¼ 7.1 Hz, 4H), 1.21 (t, J ¼ 7.1 Hz, 6H).
2
8
of the PSC is 4 mm . J–V curves were recorded with a computer-
Thieno[2,3-f]benzofuran-4,8-dione (3).
A
solution of
controlled Keithley 236 digital source meter. A xenon lamp with compound 2 (8.36 g, 50 mmol) in dry anhydrous THF (200 mL)
an AM1.5G lter was used as a white-light source and the optical was deoxygenated with argon for 15 min. Then the solution was
power was 100 mW cm . All the fabrication and characteriza- cooled to ꢀ78 ꢁC, n-BuLi (21.87 mL, 52.5 mmol) was added
ꢀ2
tions aer the cleaning of the ITO substrates were performed in dropwise within 5 min. The reaction mixture was stirred for 15
a glove box.
.4 Fabrication of OFET devices
min, and then freshly distilled thiophene-3-carboxaldehyde
5.88 g, 52.5 mmol) in THF (75 mL) was added dropwise within
(
1
5 min. The reaction mixture was stirred for another 2 h at ꢀ78
2
ꢁ
C, and a solution of n-BuLi (21.87 mL, 52.5 mmol) was added to
the reaction mixture. Aer that, the reaction mixture was
warmed up to room temperature and stirred overnight. The
reaction solution was poured into 200 mL water and extracted
Thin-lm OFETs were fabricated with a bottom-gate/top-contact
conguration. Heavily p+ doped silicon wafer substrates (Si-
Mat, Germany) covered with a thermally grown 300 nm SiO
layer were used as the gate, of which the capacitance was 10 nF
2
with CH
lation under reduced pressure. Aer cooling, the solid precipi-
tate was recrystallized in C OH and aer ltration gave
2 2
Cl ; then the extractions were concentrated by distil-
ꢀ
2
cm . The substrates were sequentially cleaned with detergent,
deionized water, acetone and ethanol in an ultrasonic bath for
2
H
5
15 min each. Subsequently, hydrophilic treatment of these
compound 3 as a yellow solid (4.7 g, 46% yield).
silicon wafers was performed according to the standard proce-
dure. Briey, the substrates were soaked in a mixture of
deionized water, 25% ammonium hydroxide and 30% H
1
H-NMR (400 MHz, CDCl ): d: 7.74 (d, J ¼ 1.8 Hz, 1H), 7.71 (d,
3
J ¼ 5.0 Hz, 1H), 7.65 (d, J ¼ 5.0 Hz, 1H), 6.97 (d, J ¼ 1.8 Hz, 1H).
2
O
2
0
4
,8-Bis(2 -ethylhexylthiophene)thieno[2,3-f]benzofuran (4). A
ꢁ
(5 : 1 : 1 by volumetric ratio) for 20 min at 80 C, then rinsed
solution of 2-(2-ethylhexyl)thiophene (3.92 g, 20 mmol) in dry
anhydrous THF (5 mL) was deoxygenated with argon for 15 min.
with deionized water and dried under a nitrogen ow. An
octadecyltrichlorosilane (OTS) self-assembled monolayer was
deposited and selected as a dielectric modication layer. Thin
polymer lms were prepared by spin coating of PTBFTDTBT
ꢁ
Then the mixture was cooled to 0 C and n-BuLi (9 mL, 21.6
mmol) was added dropwise. Aer that, the reaction was reuxed
ꢁ
for 1.5 hours at 50 C. Then SnCl
2
–2H
2
O (14.5 g, 64 mmol) in
ꢀ
1
(
8 mg mL ) in ODCB onto the OTS modied substrates at a
25.6 mL of 10% hydrogen chloride acid was added to the
speed of 2000 rpm (revolutions per minute) for 50 s at room
temperature. With or without annealing at 150 C under
atmosphere for 10 min, gold lm (50 nm) was deposited on the
organic layer to form the drain and source electrodes, for a
typical device. The drain–source channel length (L) and width
solution, and the mixture was vigorously stirred for an addi-
tional 1.5 hours. The reaction solution was then poured into
ꢁ
water (100 mL), extracted with CH
with water, saturated aqueous NaHCO
2
Cl
2
, and sequentially washed
, aqueous 1 M Na SO
3
3
2
and water. Aer the solvent was removed under vacuum, the
residue was puried by column chromatography (silica gel, PE)
(W) were 80 mm and 1000 mm, respectively. OFET measurements
were performed at room temperature using a Keithley 4200 SCS
semiconductor parameter analyzer under ambient conditions.
to give compound 4 as a pale yellow oil (1.85 g, 41% yield).
1
H-NMR (400 MHz, CDCl ): d: 7.92 (d, J ¼ 5.7 Hz, 1H), 7.78 (d,
3
J ¼ 2.3 Hz, 1H), 7.51 (t, J ¼ 5.3 Hz, 1H), 7.49–7.44 (m, 2H), 7.22
2.4 Synthesis of the monomer and polymer
(
d, J ¼ 2.3 Hz, 1H), 6.92 (dd, J ¼ 7.7, 4.7 Hz, 2H), 2.93–2.84 (m,
Furan-3-carbonyl chloride (1). 3-Furoic acid (25.1 g, 0.224 4H), 1.71 (dd, J ¼ 11.9, 5.9 Hz, 2H), 1.53–1.27 (m, 16H), 1.04–
mol) and thionyl chloride (SOCl ) (65.3 mL, 0.9 mol) were put 0.87 (m, 12H).
2
0
2,6-Bis(trimethyltin)-4,8-bis(2 -ethylhexylthiophene)thieno-
into a dry three-necked round bottomed ask. The mixture was
ꢁ
stirred at 70 C for 4 h. It was then cooled to room temperature [2,3-f]benzofuran (M1). A solution of compound 4 (1.126 g,
and the redundant solvent was removed under vacuum to give 2 mmol) in dry anhydrous THF (5 mL) was deoxygenated with
ꢁ
compound 1, a brown oil, which was used in the next step argon for 15 min. The mixture was cooled to ꢀ78 C and n-BuLi
without further purication.
(3.0 mL, 7.0 mmol) was added dropwise. The reaction mixture
N,N-diethylfuran-3-carboxamide (2). Diethylamine (92.6 mL) was stirred for 1 hour at ꢀ78 ꢁC, then warmed to room
ꢁ
and dichloromethane (100 mL) were mixed in a three-necked temperature for 1 hour, and then cooled again to ꢀ78 C; tri-
round-bottomed ask. Then, furan-3-carbonyl chloride (1) methyl tin chloride (8.0 mL, 8.0 mmol) was added, and the
ꢁ
(
29.24 g, 224 mmol) was added dropwise at 0 C. The reaction reaction mixture was allowed to warm up to room temperature
mixture was warmed up to room temperature and stirred for and stirred overnight. Aer that, the mixture was poured into
h. Then the reaction mixture was poured into 100 mL of ice- water (100 mL), extracted with CH Cl , and washed with water,
1
2
2
This journal is © The Royal Society of Chemistry 2014
J. Mater. Chem. C, 2014, 2, 5651–5659 | 5653