Effects of substituents and molecular weights on optical, thermal, and photovoltaic
properties of alternating dithienogermole-dithienylbenzothiadiazole polymers
Fei-Bao Zhang,1 Joji Ohshita,1,* Masayuki Miyazaki,1 Daiki Tanaka,1 Yasushi
Morihara2
1
Department of Applied Chemistry, Graduate School of Engineering, Hiroshima
University, Higashi-Hiroshima 739-8527, Japan and 2Synthesis Research Laboratory,
Kurashiki Research Center, Kuraray Co., Ltd., 2045-1 Sakazu, Kurashiki 710-0801,
Japan
SUPPORTING INFORMATION
EXPERIMENTAL DETAILS
General.
All reactions were carried out in dry nitrogen or argon.
Chlorobenzene used as a
reaction solvent was distilled from calcium hydride and stored over activated molecular
Starting compounds, DTGSn,1 3,6-bis(5-bromo-2-thienyl)-
sieves before use.
(TBTBr),2
benzothiadiazole
benzothiadiazole
thiadiazole
(TBT(2EH)Br),3
(TBT(Hex)Br),4
3,6-bis[5-bromo-4(2-ethylhexyl)-2-thiophenyl]2,6-bis(5-bromo-4-hexyl-2-thiophenyl)benzo-
3,6-bis[3-(2-ethylhexyl)-2-thiophenyl]benzothiadiazole
(TBT(2EH)’)5 were prepared according to the literature method.
NMR spectra were recorded on Varian 400-MR and System 500 spectrometers. The
polymer spectra are presented below.
U-2910 spectrometer.
UV-Vis spectra were measured with a Hitachi
Polymer molecular weights were measured by gel permeation
chromatography (GPC) using serially connected Shodex KF804 and KF806 columns
and THF as an eluent. The polymers were detected by a UV detector at 240 nm and the
molecular weights were calculated relative to the polystyrene standards on a SIC-480
data station.
TGA was carried out on a SIC model TG/DTA-6200 analyzer under a
gentle nitrogen flow at a heating rate of 10 ºC/min.
Fabrication and evaluation of
BHJ-PSCs with the present DTG-TBT polymers were performed as reported in the
literature.6
Preparation of TBT(2EH)Br’.
To a stirred solution of TBT(2EH)’ (0.53 g, 1.0 mmol) in chloroform-acetic acid (1:1
v/v 50 mL) was added NBS (0.360 g, 2.05 mmol) in a few portions, and the mixture
was stirred at room temperature for 4 hours then hydrolyzed with water.
After addition
of methylene chloride (50 mL), the organic layer was separated, washed with water, and
dried over anhydrous Mg2SO4.
The solvent was evapolated and the residue was
dissolved in a small amount of chloroform and poured into methanol to precipitate
TBT(2EH)Br’ as yellow solids that was separated by filtration and washed thoroughly
with methanol (0.51 g, 75%): 1H NMR (500 MHz, δ in CDCl3) 7.61 (s, 2H), 7.02 (s,
2H), 2.51 (br, 4H), 1.45 (br, 2H), 0.97-1.19 (m, 16H), 0.74 (t, 6H), 0.64 (t, 6H);
13
C
NMR (125 MHz, δ in CDCl3) 153.3, 140.8, 131.7, 130.7, 125.3, 114.6, 112.7, 38.9, 34.7,
32.4 28.7, 25.6, 23.0, 14.1, 11.0.
Preparation of polymers with alkyl-substituted TBT units.
In a 50 mL two-necked flask was placed DTGSn (0.295 g, 0.374 mmol), TBT(2EH)Br
(0.252 g, 0.369 mmol), Pd2(dba)3 (6.9 mg, 0.0075 mmol), (o-Tol)3P (11.5 mg, 0.0378
mmol), and 15 mL of chorobenzene and the mixture was heated to reflux for 5 days.
The resulting precipitates were filtered and washed with chloroform.
The filtrate was
stirred at 80 ºC for 2 h with 30 mL of an aqueous solution of sodium
N,N-diethyldithiocarbamate trihydrate
(10 wt%). The organic layer was separated
and washed with water, 3 % acetic acid (aq), then water again.
After drying of the
organic layer with anhydrous magnesium sulfate, the solvents were evaporated and the
residue was reprecipitated from chloroform/methanol to provid pDTG-TBT(2EH) as
black solids (333 mg, 91%): mp > 300°C; 1H NMR (400 MHz, δ in CDCl3) 7.99 (s, 2H),
7.86 (s, 2H), 7.23 (s, 2H), 2.85 (d, J = 8.5 Hz, 4H), 1.82 (m, 2H), 1.48-1.16 (m, 38H),
0.96-0.78 (m, 24H); 13C NMR (125 MHz, δ in CDCl3) 157.08, 152.64, 146.39, 144.75,
139.35, 136.52, 133.63, 131.26, 129.22, 125.40, 125.14, 40.13, 37.03, 35.53, 33.88,
32.63, 29.01, 28.76, 28.73, 25.80, 23.13, 23.06, 20.80, 14.21, 14.19, 10.90, 10.81.
Other DTG-TBT alternate polymers were prepared as above.
Data for
pDTG-TBT(Hex): Black solids; mp > 300°C; 1H NMR (δ in CDCl3, 500 MHz) 8.01 (s,
2H), 7.84 (s, 2H), 7.23 (s, 2H), 2.90 (s, 4H), 1.79 (s, 4H), 1.49 (s, 2H),1.44-1.18 (m,
32H), 0.97-0.82 (m, 18H);
13
C NMR (δ in CDCl3, 125 MHz) 152.61, 146.31, 144.88,
140.08, 136.61, 136.50, 133.11, 130.77, 128.88, 125.35, 125.09, 37.06, 35.57, 31.74,
30.53, 29.80, 29.37, 29.04, 28.78, 23.07, 22.68, 20.84, 14.22, 14.14, 10.93.
Data for pDTG-TBT(2EH)’: black solid; 60 % yield; mp > 300ºC; 1H NMR (500 MHz,
δ in CDCl3) 7.70 (br, 2H), 7.20 (br, 2H), 7.13 (br, 2H), 2.65 (br, 4H), 1.55 (br, 2H),
1.41-1.05 (m, 38H), 0.92-0.65 (m, 24H).
Preparation of pDTG-TBT1.
A mixture of DTGSn (0.196 g, 0.248 mmol) purified by preparative GPC, TBTBr
(0.113 g, 0.248 mmol), Pd2(dba)3 (4.7 mg, 0.0052 mmol), P(o-Tol)3 (7.9 mg, 0.026
mmol), and 10 mL of chlorobenzene was placed in a 30 mL two-necked flask and the
reaction mixture was heated to reflux for 5 days.
filtered and washed with chloroform.
The resulting precipitates were
The filtrate was stirred at 80 ºC for 2 h with 30
mL of an aqueous solution of sodium N,N-diethyldithiocarbamate trihydrate
(10 wt%).
The organic layer was separated and washed with water, 3 % acetic acid (aq), then water
again.
After drying the organic layer with anhydrous magnesium sulfate, the solvents
were evaporated and the residue was reprecipitated from chloroform/methanol to
provide polymeric substances. The polymeric substances were placed in a Soxhlet
apparatus and washed with hot methanol, acetone and hexane.
Finally the residue
remaining insoluble in those hot solvents was extracted with hot chloroform.
The
chloroform solution was poured into methanol and the precipitates were collected to
give pDTG-TBT1 (98.2 mg, 52 %) as black solids.
NMR spectra obtained for
pDTG-TBT1 were consistent with those of pDTG-TBT0, reported previously.6
REFERENCES
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and
H2O
CHCl3
1
H NMR of pDTG-TBT(2ET) in CDCl3
CDCl3
13
C NMR of pDTG-TBT(2ET) in CDCl3
H2O
CHCl3
1
H NMR of pDTG-TBT(Hex) in CDCl3
CDCl3
13
C NMR of pDTG-TBT(Hex) in CDCl3
CHCl3
1
H NMR of pDTG-TBT(2ET)’ in CDCl3
CHCl3
1
H2O
H NMR of pDTG-TBT1 in CDCl3
H2O