Tetrathienoanthracene-Based Copolymers for Efficient Solar Cells
Supporting Information for: Tetrathienoanthracene-Based Copolymers for Efficient Solar Cells
Feng He, † Wei Wang, † Wei Chen, ‡ Tao Xu, † Seth B. Darling, ‡ Joseph Strzalka, § Yun Liu┴,╒ and Luping Yu*,†
Department of Chemistry and The James Franck Institute, The University of Chicago, 929 E 57th Street, Chicago, IL 60637, USA
†
‡
Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL, 60439, USA
§
X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL, 60439, USA ┴
NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA ╒
Department of Chemical Engineering, University of Delaware, Newark, DE, 19716, USA
To whom correspondence should be addressed. E-mail: [email protected]
1. Methods and Materials. Otherwise stated, all of the chemicals are used as received from Aldrich. THF and toluene were distilled under nitrogen protection from Na/benzophenone before reaction. 1
H NMR spectra were recorded on Bruker DRX-400 or DRX-500 spectrometers with
deuterated chloroform, dichloromethane and 1,1,2,2,-tetrachloroethane, respectively. Molecular weights and distributions of polymers were determined by using a Waters GPC liquid chromatograph equipped with a Waters 515 HPLC pump, a Waters 2414 refractive index detector, and a Waters 2489 UV/Visible detector. Polystyrene standards (Aldrich) were used for calibration, and THF was used as the eluent.
S1
2. Synthesis Procedures.
Scheme S1. Synthetic routes for monomers. C 4H 9
HO
PPh3, Br 2
C6H13
Br
Br
CH2Cl2
Thiophene
S
CH o 1 6 13 n-BuLi, -78 C S
Br
I 2, H2SO4
Br
C4H9
I
I
130 oC
4
2
o C6H13 n-BuLi, -78 C Bu3Sn Bu3SnCl C 4H9
C 6H13 C4H9
3 Br
SnBu3
S
S
Pd(PPh3)2Cl2 DMF, 80 oC
Br
S
Br
5
S Br
Bu3Sn
S
C6H 13 Pd(PPh3)2Cl2
S
+
S 5
C 4H 9
Br
DMF, 130 oC
3
S
FeCl3
C4H9
S
C6H 13 CH2Cl2 C4H9 C 4H9
S S 7
S S
C6H 13
Br
C6H13
Br
S
S
S
S
NBS
C4H9
6
Br
C6H13
C6H13
C6H 13
S
C4H9
Me3Sn
C4H 9 n-BuLi, -78 oC Me3SnCl
C 4H 9
Br
C6H13 S
S
S
S SnMe3
C 6H13
8
C4H9
9
Scheme S2. Synthetic routes for PTAT-x family polymers. R1 Me 3Sn n
S S
S
R1 Br + n
S
F
S
R1
SnMe 3
S
Br
S
Pd(PPh3)4
S
S o
S
Toluene, DMF, 120 C
S
COOEH
S
F
R1
n
COOEH
PTTATT-X PTAT-1: R1 = 2-ethylhexyl PTAT-2: R1 = 2-decyltetradecyl PTAT-3: R1 = 2-butyloctyl PTAT-4: R1 = 2-ethyldodecyl
Scheme S3. Synthetic routes for polymer PTB-8.
n Me3Sn
S
OR1
Br S
SnMe 3 + n
OR1
F
S
Br S
COOEH
Pd(PPh3)4 Toluene, DMF, 120 oC
S
OR1 S S OR1
F
S
n
COOEH
R1 = 2-butyloctyloxy PTB-8
S2
2-Butyl-1-octylbromide (1) Bromine (200 mmol, 10.23 ml) was added into a solution of triphenylphosphine (200 mmol, 52.36 g) and 300 ml dichloromethane at room temperature under argon protection. Then 2-butyl-1-octanol (200 mmol, 37.27 g) was added dropwise via additional funnel over 30 minutes, the reaction solution was kept to stir at room temperature overnight. Dichloromethane was evaporated, and the concentrate filtered with pentane wash. The filtrate was concentrated via rotary evaporation and the resulting crude yellow oil was purified via vacuum distillation. The title compound was collected as colorless oil (42.7 g, 85.7 %). 1H NMR (500 MHz, CDCl3) δ: 3.45 (d, 2H, J = 4.5), 1.60 (m, 1H), 1.28 (m, 16H), 0.89 (m, 6H). 2-(2'-Butyl-1'-octyl)thiophene (2)
n-Butyl lithium (75.75 mmol, 30.3 ml 2.5 M in
hexane) was added dropwise to thiophene (0.84 g, 10 mmol) in 75 ml dry THF at -78 ºC and the solution was stirred at -78 ºC for 2 h. After that, 1 (75 mmol, 6.31 g) was added by syringe and the solution was heated to 60 ºC and stirred at this temperature for another 12 h. The reaction mixture was diluted with ether (100 mL) and washed with brine (2 x 20 ml) and dried over anhydrous Na2SO4. After concentration by rotary evaporation, the residue was purified by vacuum distillation to give the title compound as a colorless liquid (8.08 g, 44.5%). 1H NMR (500 MHz, CDCl3) δ: 7.10 (d, 1H, J = 3.5), 6.92 (m, 1H, J = 3.5), 6.75 (d, 1H, J = 3.5), 2.76 (d, 2H, J = 6.5), 1.62 (m, 1H), 1.28 (m, 16H), 0.88 (m, 6H). 2-(5-2'-Butyl-1'-octyl)tri-n-butylstannyl thiophene (3) Under a argon atmosphere, a solution of 2 (25 mmol, 6.31 g) in dry THF was cooled to -78 oC, then n-butylhhium (30 mmol, 12 ml 2.5 M in hexane) was added dropwise. The solution was stirred at -78 ºC for 1 h and then was warmed to room temperature for 30 minutes. After the solution was cooled to -78 ºC again, tributylstannyl chloride (33 mmol, 10.74 g) was added dropwise and the reaction mixture was stirred for 1 hour at -78 ºC, then allowed to warm to room temperature over another 12 h. The reaction was quenched with water (100 ml) and an organic layer separated. The aqueous layer was extracted with ether (3 x 50 ml) and the combined organic extracts were dried with anhydrous Na2SO4 and concentrated by rotary evaporation to give yellow oil. This oil was directly used for next step without further S3
purification. (100%). 1H NMR (500 MHz, CDCl3) δ: 6.98 (d, 1H, J = 2.8), 6.87 (d, 1H, J = 2.8), 2.80 (d, 2H, J = 6.4), 1.62 (m, 1H), 1.55-0.1.05 (m, 35H), 0.92-0.87 (m, 15H). 1,4-Dibromo-2,5-diiodobenzene (4) 1,4-dibromobenzene (23.6 g, 100 mmol) was dissolved in 300 mL concentrated sulfuric acid and heated to 60 oC, then iodine (55.9 g, 220 mmol) was added to the solution portion wise. The resulting purple mixture was stirred at 130 oC for 2 days during which the sublimed iodine was intermittently washed back into the reaction mixture by shaking the flask every 4 hours. The resulting mixture was cooled to room temperature and poured into ice water (300 mL), and extracted with dichloromethane (3 x 30 mL). The dichloromethane layer was then stirred with a dilute solution of sodium hydroxide (300 mL) in order to remove any excess iodine. The dichloromethane layer was separated and the aqueous sodium hydroxide layer was extracted once with dichloromethane (30 mL), and the combined organic layers were dried over anhydrous Na2SO4, evaporated, and dried under vacuum. A large portion of the product remained as a solid mass in the original reaction mixture which was broken up, triturated with dilute sodium hydroxide solution (350 mL), and filtered. Both portions combined gave a yellow solid which was recrystallized from benzene. Yield (37.5 g, 78.5%).1H NMR (500 MHz, CDCl3) δ: 8.04 (s, 2H). 1,4-bis(2-thienyl)-2,5-dibromobenzene (5) Under a argon atmosphere, 4 (9.75 g, 20 mmol) and Pd(PPh3)2Cl2 (0.562 g, 0.8 mmol) in DMF (70 mL) was syringed 2tributylstannylthiophene (15.4 g, 40 mmol) at once and the reaction stirred at 80 oC for 2 days, then allowed to cool to room temperature. All of the liquid was removed by vacuum evaporation at 130 oC, and the the residue was recrystallized from methanol (5.6 g, 70 %). 1H NMR NMR (500 MHz, CDCl3) δ: 7.80 (s, 2H), 7.44 (d, 2H, J = 5.0 Hz), 7.36 (d, 2H, J = 3.5 Hz), 7.14 (m, 2H,J = 3.5 Hz). 1,4-Bis(5-(2'-Butyl-1'-octyl)-2-thienyl)-2,5-bis(2-thienyl)benzene (6) Under a argon atmosphere, 5 (2.4 g, 6 mmol) and Pd(PPh3)2Cl2 (0.252 g, 0.24 mmol) in DMF (40 mL) was syringed 3 (15 mmol) at once and the reaction stirred at 130 oC for 2 days, then allowed to cool to room temperature. All of the liquid was removed by vacuum S4
evaporation at 130 oC, and the the residue was purified by column chromatography (silica gel, Hexanes) to yield white solid product (3.85 g, 86 %). 1H NMR NMR (500 MHz, CDCl3) δ: 7.62 (s, 2H), 7.29 (d, 2H, J = 4.5 Hz), 6.98 (m, 4H), 6.74 (d, 2H, J = 3.5 Hz), 6.61 (d, 2H,J = 3.5 Hz), 2.70 (d, 4H, J = 7), 1.57 (m, 2H), 1.26 (m, 32H), 0.89 (m, 12H). 1,4-Bis(5-(2'-Butyl-1'-octyl)-2-thienyl)-2,5-bis(5-bromo-2-thienyl)benzene (7) Under a argon atmosphere, to a solution of 6 (2.23 g, 3 mmol) in THF (120 mL) was added NBS (1.20 g, 6.72 mmol) dropwise and the reaction stirred in the dark at room temperature for another 12 h. Then the reaction solution was diluted by ether and washed with NaHCO3, brine and dried by anhydrous Na2SO4. The organic layer was concentrated by rotary evaporation and further purified by column chromatography (silica, Hexanes) to provide 7 as a light yellow sticking liquid (2.25 g, 83.2 %). 1H NMR NMR (500 MHz, CDCl3) δ: 7.54 (s, 2H), 6.92 (d, 2H, J = 3.5 Hz), 6.76 (d, 2H, J = 3.5 Hz), 6.65 (d, 2H,J = 3.5 Hz), 2.73 (d, 4H, J = 7), 1.60 (m, 2H), 1.28 (m, 32H), 0.89 (m, 12H). 2,9,-dibromo-5,12-di(2'-Butyl-1'-octyl)trithieno[2',3':5,6:3',2':3,4:3',2':7,8]anthrax[1,2,b]thiophene (8) Under a argon atmosphere, a solution of iron (III) chloride (2.42 g, 15.0 mmol) in dichloromethane (50 mL) was added dropwise to a solution of 7 (2.25 g, 2.5 mmol) in dichloromethane (400 mL). After 30 min, methanol (1000 mL) was added and the reaction solution was stirred for 30 min. The product was collected by filtration and rinsed with water and methanol. Recrystallization from hexane afforded 8 as a yellow solid (875 mg, 39%). 1H NMR NMR (500 MHz, CDCl3) δ: 8.54 (s, 2H), 7.65 (s, 2H), 7.27 (s, 2H), 2.98 (d, 4H, J = 7), 1.82 (m, 2H), 1.40 (m, 32H), 0.93 (t, 6H), 0.89 (t, 6H). 2,9-Bis(trimethyltin)-5,12-di(2'-Butyl-1'-octyl)trithieno[2',3':5,6:3',2':3,4:3',2':7,8]anthra[1,2-b]thiophene (9) 8 (0.72 g, 0.80 mmol) was dissolved in 30 mL of anhydrous THF and cooled to - 78 oC under Argon protection. Butyllithium solution (0.8 mL, 2 mmol) was added dropwise with stirring. The mixture was kept in a dry ice bath for 1 h and then at room temperature for another half hour. Then the mixture was cooled to - 78 o
C again, and 1.2 mL (1.2 mmol) of trimethyltin chloride solution (1 M in hexane) was
added by syringe and slowly warm to room temperature to keep stirring for another 12 h. S5
After that, the reaction was quenched with 50 mL of water and extracted with ether. The organic extraction was dried with anhydrous Na2SO4 and evaporated in vacuo. Recrystallization of the residue from isopropanol and hexanes yields the titled compound as yellow solid (0.54 g, 63 %). 1H NMR (500 MHz, CD2Cl2) δ: 8.88 (s, 2H), 7.86 (s, 2H), 7.53 (s, 2H), 3.06 (d, 4H, J = 8.5), 1.90 (m, 2H), 1.45 (m, 32H), 0.96 (m, 12H), 0.56 (s, 18H). Synthesis of polymer PTAT-3 2'-ethylhexyl-6-dibromo-3-fluorothieno[3,4-b]thiophene2-carboxylate (70.9 mg, 0.15 mmol), which was synthesized according our previous report, was weighted into a 25 mL one-neck round-bottom flask. Compound 9 (159.7 mg, 0.15 mmol) and Pd(PPh3)4 (7.45 mg) were added. The flask was subjected to three successive cycles of vacuum followed by refilling with argon. Then anhydrous DMF (0.45 mL) and anhydrous toluene (1.8 mL) were added via a syringe. The polymerization was carried out at 120 oC for 1 day under argon protection. The raw product was precipitated into methanol and collected by filtration. The precipitate was dissolved in chloroform and filtered through Celite to remove the metal catalyst. The crude polymer was washed with methanol, hexanes and acetone in a Soxhlet apparatus to remove the oligomers. Finally the polymer was extracted with chloroform. The polymer solution was condensed to about 5 mL and slowly poured in methanol (150 mL). The precipitate was collected and dried by vacuum overnight to yield PTAT-3 (149 mg, 94.4%). 1H NMR (400 MHz, CD2ClCD2Cl, 373 K) δ: 8.50-8.00 (br, 2H), 7.80-6.50 (br, 4H), 4.75-4.25 (br, 2H), 3.50-2.85 (br, 4H), 2.50-0.60 (br, 61H); GPC: Mw = 46.3 × 103 g/mol, PDI = 2.56. PTAT-2. 1H NMR (400 MHz, CD2ClCD2Cl, 373 K) δ: 9.00-8.30 (br, 2H), 8.00-7.00 (br, 4H), 4.70-4.30 (br, 2H), 3.30-2.2.90 (br, 4H), 2.20-0.70 (br, 101H); GPC: Mw = 39.8 × 103 g/mol, PDI = 1.65. PTAT-4. 1H NMR (400 MHz, CD2ClCD2Cl, 373 K) δ: 8.20-7.90 (br, 2H), 7.70-6.80 (br, 4H), 4.75-4.25 (br, 2H), 3.50-2.80 (br, 4H), 2.40-0.60 (br, 69H); GPC: Mw = 45.3 × 103 g/mol, PDI = 2.49.
S6
PTB-8. 1H NMR (400 MHz, CD2ClCD2Cl, 373 K) δ: 8.10-7.20 (br, 2H), 4.60-4.00 (br, 6H), 2.15-0.90 (br, 61H); GPC: Mw = 170.8 × 103 g/mol, PDI = 2.05. 3. Device Fabrication. The polymers were co-dissolved with PC61BM in chloroform, chlorobenzene (CB) and 1,2-dichlorobenzene (DCB) with or without 2% (v/v) 1,8-diiodooctance in the weight ratio of 1:1, respectively. Polymer’s concentrations are normally 10 mg/mL. ITO-coated glass substrates (15 Ω/sq) were cleaned stepwise in detergent, water, acetone, and isopropyl alcohol under ultrasonication for 15 min each and subsequently dried in an oven for 1 min at 80 oC under vacuum. Then after treated by a ultraviolet ozone for 20 min, a thin layer of PEDOT:PSS was spin-coated onto ITO surface at 4000 rpm. After being baked at 80 °C for ∼45 min under vacuum, the polymer/PCBM composites layer was then spin-cast from the blend solutions on this substrate. The spin coating speed is changed based on the solvent used, for chloroform normally at 2500 rpm, under which we got the highest power conversion efficiency in the work; for CB and DCB normally at 1000 rpm. Then the prepared device was transferred into a nitrogen-filled glovebox, which was installed with a thermal evaporator inside. A Ca layer (20 nm) and an Al layer (60 nm) were deposited in sequence under the vacuum of 2 × 10-6 torr. The effective area of film was measured to be 0.0314 cm2. The current density-voltage (J-V) curves were measured using a Keithley 2420 source-measure unit. The photocurrent was measured under AM 1.5 G illumination at 100 mW/cm2 under the Newport Oriel Sol3A Class AAA Solar Simulators 450W solar simulator (Model: 94023A, 2 in. × 2 in. beam size).
4. Instrumentation. UV-Vis Absorption and Cyclic Voltammetry. The optical absorption spectra were taken by a Shimadzu UV-2401PC spectrophotometer. Cyclic voltammetry (CV) was used to study the electrochemical properties of the polymers. For calibration, the redox potential of ferrocene/ferrocenium (Fc/Fc+) was measured under the same conditions, and it is located at 0.06 V to the Ag/Ag+ electrode. It is assumed that the redox potential of Fc/Fc+ has an absolute energy level of -4.80 eV to vacuum. The energy levels of the highest
S7
(HOMO) and lowest unoccupied molecular orbital (LUMO) were then calculated according to the following equations:
EHOMO (ox 4.74) eV; ELUMO (red 4.74) eV where φox is the onset oxidation potential vs Ag/Ag+ and φred is the onset reduction potential vs Ag/Ag+. Hole Mobility. Hole mobility was measured according to previous reports, using a diode configuration of ITO/PEDOT(poly(ethylenedioxythiophene):PSS(poly(styrenesulfonate)/ polymer/Al by taking current-voltage current in the range of 0-6 V and fitting the results to a space charge limited form, where the space charge limited current (SCLC) is described by J 9 0 r V 2 / 8L3 , where ε0 is the permittivity of free space, εr is the dielectric constant of the polymer, µ is the hole mobility, V is the voltage drop across the device (V = Vappl – Vr – Vbi, Vappl: the applied voltage to the device; Vr: the voltage drop due to contact resistance and series resistance across the electrodes; Vbi: the built-in voltage due to the difference in work function of the two electrodes), and L is the polymer film thickness. The resistance of the device was measured using a blank configuration ITO/PEDOT:PSS/Al and was found to be about 10-20 Ω. The Vbi was deduced from the best fit of the J0.5 vs Vappl plot at voltages above 2.5 V and is found to be about 1.5 V. The dielectric constant, εr, is assumed to be 3 in our analysis, which is a typical value for conjugated polymers. The thickness of the polymer films is measured by using AFM. Grazing Incidence Wide-Angle X-ray Scattering (GIWAXS) Measurements. GIWAXS measurements were performed using Beamline 8ID-E at Advanced Photon Source (APS), Argonne National Laboratory. Scattering intensities are expressed as a function of the scattering vector, q = 4π/λ sin θ, where θ is the half scattering angle and λ = 1.6868 Å is the wavelength of the incident radiation. The d-spacing of a peak is expressed by 2π/q. A two-dimensional area detector was used to collect the scattering images and was situated at 200.4 or 158.6 mm from the sample for GIWAXS measurements. The films were illuminated by X-rays at 7.35 keV at an incidence angle of about 0.2°, which is above the
S8
critical angle of both homopolymers and polymer/PC61BM blends and blow the critical angle of Si substrate. Thus, X-ray beam could penetrate the entire thickness of the film. Small Angle Neutron Scattering (SANS) Measurements. SANS measurements were performed on thin films of polymer/PC61BM blends with a film thickness of ~100 nm at the NG7 30m SANS instrument at the National Institute of Standards and Technology in Gaithersburg, MD (see reference 1 for details of instrument design and operation). Neutrons of wavelength λ = 6 Å with full width half-maximum Δλ/λ = 0.11 were used. Three configurations were used: one with the detector offset by 20 cm and a sampledetector distance of 1 m, the second with a sample-detector distance of 4 m, and the third with a sample-detector distance of 13 m, to give a scattering vector (q) range of 0.00360.5669 Å-1. The incident neutron beam was perpendicular to the films. The scattered intensity was corrected for instrument dark current, empty cell scattering, the sensitivity of individual detector pixels, and beam transmission to obtain the absolute neutron intensity by use of the available data reduction macros based on the Igor Pro data analysis package2 through the direct beam flux method. Data were analyzed by the smeared Beaucage model using the SANS analysis package provided by NCNR, NIST.
S9
5.
1
H NMR Spectra of the monomers, cyclic voltammograms of PTAT-3 films and GIWAXS 2D patterns of PTAT-3 and PTB-8 films as well as their corresponding out-of-plane and in-plane linecuts. Me 3Sn
C4H9 C6H13
C6H13 S
S
S
S
C4H9
SnMe3
Figure S1.The 1H NMR spectrum of 2,9-Bis(trimethyltin)-5,12-di(2'-butyl-1' octyl)trithieno[2',3':5,6:3',2':3,4:3',2':7,8]- anthra[1,2-b]thiophene.
S10
C10H21
Me3Sn
C2H5 C10H21
S
S
S
S
C2H5
SnMe3
Figure S2.The 1H NMR spectrum of 2,9-Bis(trimethyltin)-5,12-di(2'-ethyl-1'dodecyl)trithieno[2',3':5,6:3',2':3,4:3',2':7,8]- anthra[1,2-b]thiophene.
S11
O Me3Sn
S S
SnMe3
O
Figure S3.The 1H NMR spectrum of 2,6-Bis(trimethyltin)-4,8-bis(2-butyloctyloxy)benzo[1,2b:4,5-b']dithiophene.
S12
S
Br
Br S
F O
O
Figure S4.The 1H NMR spectrum of 2'-Ethylhexyl-4,6-dibromo-3-fluorothieno[3,4-b]thiophene2-carboxylate.
S13
Onset = -1.46 V LUMO = -3.28 eV
Current (mA)
0.02
0.00
Onset = 0.30 V HOMO = -5.04 eV
-0.02
-0.04
-0.06 1000
500
0
-500
-1000
-1500
-2000
Voltage (mV)
Figure S5. Cyclic voltammograms (50 mV s-1) of PTAT-3 film cast on a platinum electrode in a 0.1 mol L-1 Bu4NPF6, CH3CN solution.
70
PTAT-3 60
EQE (%)
50 40 30 20 10 0 400
500
600
700
800
Wavelength (nm)
Figure S6. EQE curve of PTAT-3/PC61BM BHJ solar cell device.
S14
A
B
12000
C
PTAT‐3 PTB‐8
2000
1000
0 0.5
1.0
1.5
D
PTAT‐3 PTB‐8
9000
Intensity (a.u.)
Intensity (a.u.)
3000
2.0
‐1
qz (Å )
6000
3000
0 0.1
0.5
1.0
1.5
2.0
2.5
‐1
qy (Å )
Figure S7. 2D GIWAXS patterns of the films of PTAT-3 (a) and PTB-8 (b); c) Out-of-plane linecuts of GIWAXS of PTAT-3 and PTB-8 films; d) In-plane linecuts of GIWAXS of PTAT-3 and PTB-8 films. Note: the profiles have been shifted vertically for clarity.
Reference (1) Glinka, C. J.; Barker, J. G.; Hammouda, B.; Krueger, S.; Moyer, J. J.; Orts, W. J. J. Appl. Cryst. 1998, 31, 430-445. (2) Kline, S. R. J. Appl. Cryst. 2006, 39, 895-900.
S15
Feng He, † Wei Wang, † Wei Chen, ‡ Tao Xu, † Seth B. Darling, ‡ Joseph Strzalka, § Yun Liu┴,╒ and Luping Yu*,†
Department of Chemistry and The James Franck Institute, The University of Chicago, 929 E 57th Street, Chicago, IL 60637, USA
†
‡
Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL, 60439, USA
§
X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL, 60439, USA ┴
NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA ╒
Department of Chemical Engineering, University of Delaware, Newark, DE, 19716, USA
To whom correspondence should be addressed. E-mail: [email protected]
1. Methods and Materials. Otherwise stated, all of the chemicals are used as received from Aldrich. THF and toluene were distilled under nitrogen protection from Na/benzophenone before reaction. 1
H NMR spectra were recorded on Bruker DRX-400 or DRX-500 spectrometers with
deuterated chloroform, dichloromethane and 1,1,2,2,-tetrachloroethane, respectively. Molecular weights and distributions of polymers were determined by using a Waters GPC liquid chromatograph equipped with a Waters 515 HPLC pump, a Waters 2414 refractive index detector, and a Waters 2489 UV/Visible detector. Polystyrene standards (Aldrich) were used for calibration, and THF was used as the eluent.
S1
2. Synthesis Procedures.
Scheme S1. Synthetic routes for monomers. C 4H 9
HO
PPh3, Br 2
C6H13
Br
Br
CH2Cl2
Thiophene
S
CH o 1 6 13 n-BuLi, -78 C S
Br
I 2, H2SO4
Br
C4H9
I
I
130 oC
4
2
o C6H13 n-BuLi, -78 C Bu3Sn Bu3SnCl C 4H9
C 6H13 C4H9
3 Br
SnBu3
S
S
Pd(PPh3)2Cl2 DMF, 80 oC
Br
S
Br
5
S Br
Bu3Sn
S
C6H 13 Pd(PPh3)2Cl2
S
+
S 5
C 4H 9
Br
DMF, 130 oC
3
S
FeCl3
C4H9
S
C6H 13 CH2Cl2 C4H9 C 4H9
S S 7
S S
C6H 13
Br
C6H13
Br
S
S
S
S
NBS
C4H9
6
Br
C6H13
C6H13
C6H 13
S
C4H9
Me3Sn
C4H 9 n-BuLi, -78 oC Me3SnCl
C 4H 9
Br
C6H13 S
S
S
S SnMe3
C 6H13
8
C4H9
9
Scheme S2. Synthetic routes for PTAT-x family polymers. R1 Me 3Sn n
S S
S
R1 Br + n
S
F
S
R1
SnMe 3
S
Br
S
Pd(PPh3)4
S
S o
S
Toluene, DMF, 120 C
S
COOEH
S
F
R1
n
COOEH
PTTATT-X PTAT-1: R1 = 2-ethylhexyl PTAT-2: R1 = 2-decyltetradecyl PTAT-3: R1 = 2-butyloctyl PTAT-4: R1 = 2-ethyldodecyl
Scheme S3. Synthetic routes for polymer PTB-8.
n Me3Sn
S
OR1
Br S
SnMe 3 + n
OR1
F
S
Br S
COOEH
Pd(PPh3)4 Toluene, DMF, 120 oC
S
OR1 S S OR1
F
S
n
COOEH
R1 = 2-butyloctyloxy PTB-8
S2
2-Butyl-1-octylbromide (1) Bromine (200 mmol, 10.23 ml) was added into a solution of triphenylphosphine (200 mmol, 52.36 g) and 300 ml dichloromethane at room temperature under argon protection. Then 2-butyl-1-octanol (200 mmol, 37.27 g) was added dropwise via additional funnel over 30 minutes, the reaction solution was kept to stir at room temperature overnight. Dichloromethane was evaporated, and the concentrate filtered with pentane wash. The filtrate was concentrated via rotary evaporation and the resulting crude yellow oil was purified via vacuum distillation. The title compound was collected as colorless oil (42.7 g, 85.7 %). 1H NMR (500 MHz, CDCl3) δ: 3.45 (d, 2H, J = 4.5), 1.60 (m, 1H), 1.28 (m, 16H), 0.89 (m, 6H). 2-(2'-Butyl-1'-octyl)thiophene (2)
n-Butyl lithium (75.75 mmol, 30.3 ml 2.5 M in
hexane) was added dropwise to thiophene (0.84 g, 10 mmol) in 75 ml dry THF at -78 ºC and the solution was stirred at -78 ºC for 2 h. After that, 1 (75 mmol, 6.31 g) was added by syringe and the solution was heated to 60 ºC and stirred at this temperature for another 12 h. The reaction mixture was diluted with ether (100 mL) and washed with brine (2 x 20 ml) and dried over anhydrous Na2SO4. After concentration by rotary evaporation, the residue was purified by vacuum distillation to give the title compound as a colorless liquid (8.08 g, 44.5%). 1H NMR (500 MHz, CDCl3) δ: 7.10 (d, 1H, J = 3.5), 6.92 (m, 1H, J = 3.5), 6.75 (d, 1H, J = 3.5), 2.76 (d, 2H, J = 6.5), 1.62 (m, 1H), 1.28 (m, 16H), 0.88 (m, 6H). 2-(5-2'-Butyl-1'-octyl)tri-n-butylstannyl thiophene (3) Under a argon atmosphere, a solution of 2 (25 mmol, 6.31 g) in dry THF was cooled to -78 oC, then n-butylhhium (30 mmol, 12 ml 2.5 M in hexane) was added dropwise. The solution was stirred at -78 ºC for 1 h and then was warmed to room temperature for 30 minutes. After the solution was cooled to -78 ºC again, tributylstannyl chloride (33 mmol, 10.74 g) was added dropwise and the reaction mixture was stirred for 1 hour at -78 ºC, then allowed to warm to room temperature over another 12 h. The reaction was quenched with water (100 ml) and an organic layer separated. The aqueous layer was extracted with ether (3 x 50 ml) and the combined organic extracts were dried with anhydrous Na2SO4 and concentrated by rotary evaporation to give yellow oil. This oil was directly used for next step without further S3
purification. (100%). 1H NMR (500 MHz, CDCl3) δ: 6.98 (d, 1H, J = 2.8), 6.87 (d, 1H, J = 2.8), 2.80 (d, 2H, J = 6.4), 1.62 (m, 1H), 1.55-0.1.05 (m, 35H), 0.92-0.87 (m, 15H). 1,4-Dibromo-2,5-diiodobenzene (4) 1,4-dibromobenzene (23.6 g, 100 mmol) was dissolved in 300 mL concentrated sulfuric acid and heated to 60 oC, then iodine (55.9 g, 220 mmol) was added to the solution portion wise. The resulting purple mixture was stirred at 130 oC for 2 days during which the sublimed iodine was intermittently washed back into the reaction mixture by shaking the flask every 4 hours. The resulting mixture was cooled to room temperature and poured into ice water (300 mL), and extracted with dichloromethane (3 x 30 mL). The dichloromethane layer was then stirred with a dilute solution of sodium hydroxide (300 mL) in order to remove any excess iodine. The dichloromethane layer was separated and the aqueous sodium hydroxide layer was extracted once with dichloromethane (30 mL), and the combined organic layers were dried over anhydrous Na2SO4, evaporated, and dried under vacuum. A large portion of the product remained as a solid mass in the original reaction mixture which was broken up, triturated with dilute sodium hydroxide solution (350 mL), and filtered. Both portions combined gave a yellow solid which was recrystallized from benzene. Yield (37.5 g, 78.5%).1H NMR (500 MHz, CDCl3) δ: 8.04 (s, 2H). 1,4-bis(2-thienyl)-2,5-dibromobenzene (5) Under a argon atmosphere, 4 (9.75 g, 20 mmol) and Pd(PPh3)2Cl2 (0.562 g, 0.8 mmol) in DMF (70 mL) was syringed 2tributylstannylthiophene (15.4 g, 40 mmol) at once and the reaction stirred at 80 oC for 2 days, then allowed to cool to room temperature. All of the liquid was removed by vacuum evaporation at 130 oC, and the the residue was recrystallized from methanol (5.6 g, 70 %). 1H NMR NMR (500 MHz, CDCl3) δ: 7.80 (s, 2H), 7.44 (d, 2H, J = 5.0 Hz), 7.36 (d, 2H, J = 3.5 Hz), 7.14 (m, 2H,J = 3.5 Hz). 1,4-Bis(5-(2'-Butyl-1'-octyl)-2-thienyl)-2,5-bis(2-thienyl)benzene (6) Under a argon atmosphere, 5 (2.4 g, 6 mmol) and Pd(PPh3)2Cl2 (0.252 g, 0.24 mmol) in DMF (40 mL) was syringed 3 (15 mmol) at once and the reaction stirred at 130 oC for 2 days, then allowed to cool to room temperature. All of the liquid was removed by vacuum S4
evaporation at 130 oC, and the the residue was purified by column chromatography (silica gel, Hexanes) to yield white solid product (3.85 g, 86 %). 1H NMR NMR (500 MHz, CDCl3) δ: 7.62 (s, 2H), 7.29 (d, 2H, J = 4.5 Hz), 6.98 (m, 4H), 6.74 (d, 2H, J = 3.5 Hz), 6.61 (d, 2H,J = 3.5 Hz), 2.70 (d, 4H, J = 7), 1.57 (m, 2H), 1.26 (m, 32H), 0.89 (m, 12H). 1,4-Bis(5-(2'-Butyl-1'-octyl)-2-thienyl)-2,5-bis(5-bromo-2-thienyl)benzene (7) Under a argon atmosphere, to a solution of 6 (2.23 g, 3 mmol) in THF (120 mL) was added NBS (1.20 g, 6.72 mmol) dropwise and the reaction stirred in the dark at room temperature for another 12 h. Then the reaction solution was diluted by ether and washed with NaHCO3, brine and dried by anhydrous Na2SO4. The organic layer was concentrated by rotary evaporation and further purified by column chromatography (silica, Hexanes) to provide 7 as a light yellow sticking liquid (2.25 g, 83.2 %). 1H NMR NMR (500 MHz, CDCl3) δ: 7.54 (s, 2H), 6.92 (d, 2H, J = 3.5 Hz), 6.76 (d, 2H, J = 3.5 Hz), 6.65 (d, 2H,J = 3.5 Hz), 2.73 (d, 4H, J = 7), 1.60 (m, 2H), 1.28 (m, 32H), 0.89 (m, 12H). 2,9,-dibromo-5,12-di(2'-Butyl-1'-octyl)trithieno[2',3':5,6:3',2':3,4:3',2':7,8]anthrax[1,2,b]thiophene (8) Under a argon atmosphere, a solution of iron (III) chloride (2.42 g, 15.0 mmol) in dichloromethane (50 mL) was added dropwise to a solution of 7 (2.25 g, 2.5 mmol) in dichloromethane (400 mL). After 30 min, methanol (1000 mL) was added and the reaction solution was stirred for 30 min. The product was collected by filtration and rinsed with water and methanol. Recrystallization from hexane afforded 8 as a yellow solid (875 mg, 39%). 1H NMR NMR (500 MHz, CDCl3) δ: 8.54 (s, 2H), 7.65 (s, 2H), 7.27 (s, 2H), 2.98 (d, 4H, J = 7), 1.82 (m, 2H), 1.40 (m, 32H), 0.93 (t, 6H), 0.89 (t, 6H). 2,9-Bis(trimethyltin)-5,12-di(2'-Butyl-1'-octyl)trithieno[2',3':5,6:3',2':3,4:3',2':7,8]anthra[1,2-b]thiophene (9) 8 (0.72 g, 0.80 mmol) was dissolved in 30 mL of anhydrous THF and cooled to - 78 oC under Argon protection. Butyllithium solution (0.8 mL, 2 mmol) was added dropwise with stirring. The mixture was kept in a dry ice bath for 1 h and then at room temperature for another half hour. Then the mixture was cooled to - 78 o
C again, and 1.2 mL (1.2 mmol) of trimethyltin chloride solution (1 M in hexane) was
added by syringe and slowly warm to room temperature to keep stirring for another 12 h. S5
After that, the reaction was quenched with 50 mL of water and extracted with ether. The organic extraction was dried with anhydrous Na2SO4 and evaporated in vacuo. Recrystallization of the residue from isopropanol and hexanes yields the titled compound as yellow solid (0.54 g, 63 %). 1H NMR (500 MHz, CD2Cl2) δ: 8.88 (s, 2H), 7.86 (s, 2H), 7.53 (s, 2H), 3.06 (d, 4H, J = 8.5), 1.90 (m, 2H), 1.45 (m, 32H), 0.96 (m, 12H), 0.56 (s, 18H). Synthesis of polymer PTAT-3 2'-ethylhexyl-6-dibromo-3-fluorothieno[3,4-b]thiophene2-carboxylate (70.9 mg, 0.15 mmol), which was synthesized according our previous report, was weighted into a 25 mL one-neck round-bottom flask. Compound 9 (159.7 mg, 0.15 mmol) and Pd(PPh3)4 (7.45 mg) were added. The flask was subjected to three successive cycles of vacuum followed by refilling with argon. Then anhydrous DMF (0.45 mL) and anhydrous toluene (1.8 mL) were added via a syringe. The polymerization was carried out at 120 oC for 1 day under argon protection. The raw product was precipitated into methanol and collected by filtration. The precipitate was dissolved in chloroform and filtered through Celite to remove the metal catalyst. The crude polymer was washed with methanol, hexanes and acetone in a Soxhlet apparatus to remove the oligomers. Finally the polymer was extracted with chloroform. The polymer solution was condensed to about 5 mL and slowly poured in methanol (150 mL). The precipitate was collected and dried by vacuum overnight to yield PTAT-3 (149 mg, 94.4%). 1H NMR (400 MHz, CD2ClCD2Cl, 373 K) δ: 8.50-8.00 (br, 2H), 7.80-6.50 (br, 4H), 4.75-4.25 (br, 2H), 3.50-2.85 (br, 4H), 2.50-0.60 (br, 61H); GPC: Mw = 46.3 × 103 g/mol, PDI = 2.56. PTAT-2. 1H NMR (400 MHz, CD2ClCD2Cl, 373 K) δ: 9.00-8.30 (br, 2H), 8.00-7.00 (br, 4H), 4.70-4.30 (br, 2H), 3.30-2.2.90 (br, 4H), 2.20-0.70 (br, 101H); GPC: Mw = 39.8 × 103 g/mol, PDI = 1.65. PTAT-4. 1H NMR (400 MHz, CD2ClCD2Cl, 373 K) δ: 8.20-7.90 (br, 2H), 7.70-6.80 (br, 4H), 4.75-4.25 (br, 2H), 3.50-2.80 (br, 4H), 2.40-0.60 (br, 69H); GPC: Mw = 45.3 × 103 g/mol, PDI = 2.49.
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PTB-8. 1H NMR (400 MHz, CD2ClCD2Cl, 373 K) δ: 8.10-7.20 (br, 2H), 4.60-4.00 (br, 6H), 2.15-0.90 (br, 61H); GPC: Mw = 170.8 × 103 g/mol, PDI = 2.05. 3. Device Fabrication. The polymers were co-dissolved with PC61BM in chloroform, chlorobenzene (CB) and 1,2-dichlorobenzene (DCB) with or without 2% (v/v) 1,8-diiodooctance in the weight ratio of 1:1, respectively. Polymer’s concentrations are normally 10 mg/mL. ITO-coated glass substrates (15 Ω/sq) were cleaned stepwise in detergent, water, acetone, and isopropyl alcohol under ultrasonication for 15 min each and subsequently dried in an oven for 1 min at 80 oC under vacuum. Then after treated by a ultraviolet ozone for 20 min, a thin layer of PEDOT:PSS was spin-coated onto ITO surface at 4000 rpm. After being baked at 80 °C for ∼45 min under vacuum, the polymer/PCBM composites layer was then spin-cast from the blend solutions on this substrate. The spin coating speed is changed based on the solvent used, for chloroform normally at 2500 rpm, under which we got the highest power conversion efficiency in the work; for CB and DCB normally at 1000 rpm. Then the prepared device was transferred into a nitrogen-filled glovebox, which was installed with a thermal evaporator inside. A Ca layer (20 nm) and an Al layer (60 nm) were deposited in sequence under the vacuum of 2 × 10-6 torr. The effective area of film was measured to be 0.0314 cm2. The current density-voltage (J-V) curves were measured using a Keithley 2420 source-measure unit. The photocurrent was measured under AM 1.5 G illumination at 100 mW/cm2 under the Newport Oriel Sol3A Class AAA Solar Simulators 450W solar simulator (Model: 94023A, 2 in. × 2 in. beam size).
4. Instrumentation. UV-Vis Absorption and Cyclic Voltammetry. The optical absorption spectra were taken by a Shimadzu UV-2401PC spectrophotometer. Cyclic voltammetry (CV) was used to study the electrochemical properties of the polymers. For calibration, the redox potential of ferrocene/ferrocenium (Fc/Fc+) was measured under the same conditions, and it is located at 0.06 V to the Ag/Ag+ electrode. It is assumed that the redox potential of Fc/Fc+ has an absolute energy level of -4.80 eV to vacuum. The energy levels of the highest
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(HOMO) and lowest unoccupied molecular orbital (LUMO) were then calculated according to the following equations:
EHOMO (ox 4.74) eV; ELUMO (red 4.74) eV where φox is the onset oxidation potential vs Ag/Ag+ and φred is the onset reduction potential vs Ag/Ag+. Hole Mobility. Hole mobility was measured according to previous reports, using a diode configuration of ITO/PEDOT(poly(ethylenedioxythiophene):PSS(poly(styrenesulfonate)/ polymer/Al by taking current-voltage current in the range of 0-6 V and fitting the results to a space charge limited form, where the space charge limited current (SCLC) is described by J 9 0 r V 2 / 8L3 , where ε0 is the permittivity of free space, εr is the dielectric constant of the polymer, µ is the hole mobility, V is the voltage drop across the device (V = Vappl – Vr – Vbi, Vappl: the applied voltage to the device; Vr: the voltage drop due to contact resistance and series resistance across the electrodes; Vbi: the built-in voltage due to the difference in work function of the two electrodes), and L is the polymer film thickness. The resistance of the device was measured using a blank configuration ITO/PEDOT:PSS/Al and was found to be about 10-20 Ω. The Vbi was deduced from the best fit of the J0.5 vs Vappl plot at voltages above 2.5 V and is found to be about 1.5 V. The dielectric constant, εr, is assumed to be 3 in our analysis, which is a typical value for conjugated polymers. The thickness of the polymer films is measured by using AFM. Grazing Incidence Wide-Angle X-ray Scattering (GIWAXS) Measurements. GIWAXS measurements were performed using Beamline 8ID-E at Advanced Photon Source (APS), Argonne National Laboratory. Scattering intensities are expressed as a function of the scattering vector, q = 4π/λ sin θ, where θ is the half scattering angle and λ = 1.6868 Å is the wavelength of the incident radiation. The d-spacing of a peak is expressed by 2π/q. A two-dimensional area detector was used to collect the scattering images and was situated at 200.4 or 158.6 mm from the sample for GIWAXS measurements. The films were illuminated by X-rays at 7.35 keV at an incidence angle of about 0.2°, which is above the
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critical angle of both homopolymers and polymer/PC61BM blends and blow the critical angle of Si substrate. Thus, X-ray beam could penetrate the entire thickness of the film. Small Angle Neutron Scattering (SANS) Measurements. SANS measurements were performed on thin films of polymer/PC61BM blends with a film thickness of ~100 nm at the NG7 30m SANS instrument at the National Institute of Standards and Technology in Gaithersburg, MD (see reference 1 for details of instrument design and operation). Neutrons of wavelength λ = 6 Å with full width half-maximum Δλ/λ = 0.11 were used. Three configurations were used: one with the detector offset by 20 cm and a sampledetector distance of 1 m, the second with a sample-detector distance of 4 m, and the third with a sample-detector distance of 13 m, to give a scattering vector (q) range of 0.00360.5669 Å-1. The incident neutron beam was perpendicular to the films. The scattered intensity was corrected for instrument dark current, empty cell scattering, the sensitivity of individual detector pixels, and beam transmission to obtain the absolute neutron intensity by use of the available data reduction macros based on the Igor Pro data analysis package2 through the direct beam flux method. Data were analyzed by the smeared Beaucage model using the SANS analysis package provided by NCNR, NIST.
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5.
1
H NMR Spectra of the monomers, cyclic voltammograms of PTAT-3 films and GIWAXS 2D patterns of PTAT-3 and PTB-8 films as well as their corresponding out-of-plane and in-plane linecuts. Me 3Sn
C4H9 C6H13
C6H13 S
S
S
S
C4H9
SnMe3
Figure S1.The 1H NMR spectrum of 2,9-Bis(trimethyltin)-5,12-di(2'-butyl-1' octyl)trithieno[2',3':5,6:3',2':3,4:3',2':7,8]- anthra[1,2-b]thiophene.
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C10H21
Me3Sn
C2H5 C10H21
S
S
S
S
C2H5
SnMe3
Figure S2.The 1H NMR spectrum of 2,9-Bis(trimethyltin)-5,12-di(2'-ethyl-1'dodecyl)trithieno[2',3':5,6:3',2':3,4:3',2':7,8]- anthra[1,2-b]thiophene.
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O Me3Sn
S S
SnMe3
O
Figure S3.The 1H NMR spectrum of 2,6-Bis(trimethyltin)-4,8-bis(2-butyloctyloxy)benzo[1,2b:4,5-b']dithiophene.
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S
Br
Br S
F O
O
Figure S4.The 1H NMR spectrum of 2'-Ethylhexyl-4,6-dibromo-3-fluorothieno[3,4-b]thiophene2-carboxylate.
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Onset = -1.46 V LUMO = -3.28 eV
Current (mA)
0.02
0.00
Onset = 0.30 V HOMO = -5.04 eV
-0.02
-0.04
-0.06 1000
500
0
-500
-1000
-1500
-2000
Voltage (mV)
Figure S5. Cyclic voltammograms (50 mV s-1) of PTAT-3 film cast on a platinum electrode in a 0.1 mol L-1 Bu4NPF6, CH3CN solution.
70
PTAT-3 60
EQE (%)
50 40 30 20 10 0 400
500
600
700
800
Wavelength (nm)
Figure S6. EQE curve of PTAT-3/PC61BM BHJ solar cell device.
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A
B
12000
C
PTAT‐3 PTB‐8
2000
1000
0 0.5
1.0
1.5
D
PTAT‐3 PTB‐8
9000
Intensity (a.u.)
Intensity (a.u.)
3000
2.0
‐1
qz (Å )
6000
3000
0 0.1
0.5
1.0
1.5
2.0
2.5
‐1
qy (Å )
Figure S7. 2D GIWAXS patterns of the films of PTAT-3 (a) and PTB-8 (b); c) Out-of-plane linecuts of GIWAXS of PTAT-3 and PTB-8 films; d) In-plane linecuts of GIWAXS of PTAT-3 and PTB-8 films. Note: the profiles have been shifted vertically for clarity.
Reference (1) Glinka, C. J.; Barker, J. G.; Hammouda, B.; Krueger, S.; Moyer, J. J.; Orts, W. J. J. Appl. Cryst. 1998, 31, 430-445. (2) Kline, S. R. J. Appl. Cryst. 2006, 39, 895-900.
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