Effect of Alkyl Side Chains of Conjugated Polymer Donors on the ...
Supporting Information
Effect of Alkyl Side Chains of Conjugated Polymer Donors on the Device Performance of Non-Fullerene Solar Cells Dongdong Xia,† Yang Wu,‡ Qiang Wang,§ Andong Zhang,† Cheng Li,*, † Yuze Lin,⊥ Fallon J. M. Colberts,§ Jacobus J. van Franeker,§ René A. J. Janssen,§ Xiaowei Zhan,⊥ Wenping Hu,† Zheng Tang,*,║ Wei Ma*,‡ and Weiwei Li*,† †
Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 10090, China. Email: [email protected], [email protected]
‡
State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, PR China. E-mail: [email protected]
§
Molecular Materials and Nanosystems & Institute for Complex Molecular Systems, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
⊥
Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, China.
║
Institut für Angewandte Photophysik, Technische Universität Dresden, George-BährStraße 1, 01069, Dresden, Germany. E-mail: [email protected]
S0
Contents 1.
Materials and measurements
2.
Synthesis of the monomers and polymers
3.
DFT calculations
4.
GPC
5.
CV measurement
6.
FETs
7.
Solar cells of PBDT2FT:[70]PCBM
8.
Solar cells of PBDT2FT:ITIC
9.
SCLC measurement
10.
TEM of PBDT2FT:ITIC
11.
NMR spectra of the monomers and polymers
12.
References
1. Materials and measurements All synthetic procedures were performed under argon atmosphere. Commercial chemicals were used as received. THF and toluene were distilled from sodium under an N2 atmosphere. [6,6]-phenyl-C71-butyric acid methyl ester ([70]PCBM) and the electron acceptor ITIC were purchased from Solarmer Materials Inc. (3,3'-difluoro-[2,2'-bithiophene]-5,5'diyl)bis(trimethylstannane)
(3)
was
purchased
from
SunaTech
hexyldecyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene (1),S
1
Inc.
4,8-bis(5-(2-
4,8-bis(5-(2-octyldodecyl)-
thiophen-2-yl)benzo[1,2-b:4,5-b']dithiopheneS 2 and 4,8-bis(5-(2-decyltetradecyl)thiophen-2yl)benzo[1,2-b:4,5-b']dithiopheneS3 were synthesized according to literature procedures. 1HNMR and 13C-NMR spectra were recorded at 400 MHz and 100 MHz on a Bruker AVANCE spectrometer with CDCl3 as the solvent and tetramethylsilane (TMS) as the internal standard. Molecular weight was determined with GPC at 140 °C on a PL-GPC 220 system using a PLGEL 10 µm MIXED-B column and o-DCB as the eluent against polystyrene standards. Low concentration of 0.1 mg mL-1 polymer in o-DCB was applied to reduce aggregation. Optical absorption spectra were recorded on a JASCO V-570 spectrometer with a slit width of 2.0 nm and a scan speed of 1000 nm min-1. Cyclic voltammetry was performed under an inert atmosphere at a scan rate of 0.1 V s-1 and 1 M tetrabutylammonium hexafluorophosphate in acetonitrile as the electrolyte, a glassy-carbon working electrode coated with samples, a platinum-wire auxiliary electrode, and an Ag/AgCl as a reference electrode.
S1
TEM was performed on a Tecnai G2 Sphera transmission electron microscope (FEI) operated at 200 kV on films floated from PEDOT:PSS coated substrates in deionized water. GIWAXS measurements were performed at beamline 7.3.3S4 at the Advanced Light Source. Samples were prepared on Si substrates using identical blend solutions as those used in devices. The 10 keV X-ray beam was incident at a grazing angle of 0.12°-0.16°, selected to maximize the scattering intensity from the samples. The scattered x-rays were detected using a Dectris Pilatus 2M photon counting detector. R-SoXS transmission measurements were performed at beamline 11.0.1.2S 5 at the Advanced Light Source (ALS). Samples for R-SoXS measurements were prepared on a PEDOT:PSS modified Si substrate under the same conditions as those used for device fabrication, and then transferred by floating in water to a 1.5 mm × 1.5 mm, 100 nm thick Si3N4 membrane supported by a 5 mm × 5 mm, 200 µm thick Si frame (Norcada Inc.). 2-D scattering patterns were collected on an in-vacuum CCD camera (Princeton Instrument PIMTE). The sample detector distance was calibrated from diffraction peaks of a triblock copolymer poly(isoprene-b-styrene-b-2-vinyl pyridine), which has a known spacing of 391 Å. The beam size at the sample is approximately 100 µm by 200 µm. The organic field-effect transistors were fabricated on a commercial Si/SiO2/Au substrate purchased from First MEMS Co. Ltd. A heavily N-doped Si wafer with a SiO2 layer of 300 nm served as the gate electrode and dielectric layer, respectively. The Ti (2 nm)/Au (28 nm) source−drain electrodes were sputtered and patterned by a lift-off technique. Before deposition of the organic semiconductor, the gate dielectrics were treated with octadecyltrichlorosilane (OTS) in a vacuum oven at a temperature of 120 °C, forming an OTS self-assembled monolayers. The treated substrates were rinsed successively with hexane, chloroform, and isopropyl alcohol. Polymer thin films were spin coated on the substrate from o-DCB solution with a thickness of around 30 – 50 nm. The devices were thermally annealed at certain temperature for 10 min in a glovebox filled with N2 before measurement. The devices were measured on a Keithley 4200 SCS semiconductor parameter analyzer at room temperature. The mobilities were calculated from the saturation region with the following equation: ISD = (W/2L)Ciµ(VG-VT)2, where ISD is the drain–source current, W is the channel width (1400 µm), L is the channel length (50 µm), µ is the field-effect mobility, Ci is the capacitance per unit area of the gate dielectric layer, and VG and VT are the gate voltage and threshold voltage, respectively. This equation defines the important characteristics of electron mobility (µ), on/off ratio (Ion/Ioff), and threshold voltage (VT), which could be deduced by the equation from the plot of current–voltage. S2
Photovoltaic devices with inverted configuration were made by spin-coating a ZnO solS6
gel at 4000 rpm for 60 s onto pre-cleaned, patterned ITO substrates. The photoactive layer was deposited by spin coating a chlorobenzene solution containing PBDT2FT and [70]PCBM (or ITIC) and the appropriate amount of DIO as processing additive in air. MoO3 (10 nm) and Ag (100 nm) were deposited by vacuum evaporation at ca. 4 × 10-5 Pa as the back electrode. For the regular device configuration, poly(ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) (Clevios P, VP AI 4083) was spin coated onto ITO substrates, following by spin coating active layers. LiF (1 nm) and Al (100 nm) were deposited by vacuum evaporation as back electrode. The active area of the cells was 0.04 cm2. The J-V characteristics were measured by a Keithley 2400 source meter unit under AM1.5G spectrum from a solar simulator (Enlitech model SS-F5-3A). Solar simulator illumination intensity was determined at 100 mW cm−2 using a monocrystal silicon reference cell with KG5 filter. Short circuit currents under AM1.5G conditions were estimated from the spectral response and convolution with the solar spectrum. The external quantum efficiency was measured by a Solar Cell Spectral Response Measurement System QE-R3011 (Enli Technology Co., Ltd.). The thickness of the active layers in the photovoltaic devices was measured on a Veeco Dektak XT profilometer. Calculation of the IQE spectra was done by taking the ratio between the measured EQE and the theoretical maximum EQE predicted by a transfer matrix model.S 7 Extinction coefficients of the active materials systems were measured by using the Beer-lambert Law, with reflection and transmission of thin film samples (deposited on glass) measured by an integrating sphere. Refractive indices were simply assumed to be 2 according to reference.S8 For modeling the theoretical maximum EQE, we used a 80 nm thick active layer for the PCBM based solar cells with a regular device structure, and a 60 nm thick active layer for the ITIC solar cells with an inverted geometry. 2. Synthesis of the monomers and polymers 2,6-dibromo-4,8-bis(5-(2-hexyldecyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene (2). n-BuLi (2.4 M hexane solution, 5.9 mL, 2.47 mmol) was added dropwise into a solution of compound 1 (0.66 g, 0.82 mmol) in 10 ml dry THF at room temperature (RT). The mixture was maintained at this temperature for 3 h. After cooled to -78 ºC, CBr4 (1.09 g, 3.29 mmol) in anhydrous THF (5 mL) was added dropwise and the mixture was stirred for another 30 min. After warmed to room temperature overnight, the mixture was poured into water (100 mL), extracted with diethyl ether (100 mL), washed with brine and dried over MgSO4. After S3
removal of the solvent, the residue was purified by silica gel chromatography (hexane) to afford compound 2 (0.48 g, 60.8%) as a yellow oil. 1H NMR δ (ppm): 7.57 (s, 2H), 7.21 (d, 2H), 6.86 (d, 2H), 2.84 (d, 4H), 1.71 (m, 2H), 1.42-1.29 (m, 48H), 0.89-0.85 (t, 12H).
13
C
NMR δ (ppm): 146.6, 140.4, 136.1, 136.1, 128.0, 126.2, 125.7, 122.6, 116.9, 40.2, 34.8, 33.5, 32.08, 32.05, 30.1, 29.81, 29.79, 29.5, 26.81, 26.80, 22.9, 14.3. MS (MALDI): calculated: 958.29, found: 960.1 (M+). 2,6-dibromo-4,8-bis(5-(2-octyldodecyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene (5). Same procedure as for 2 was used, but now 4 (0.51 g, 0.56 mmol) was used as the reactants. Yield: 0.42 g (70.3%). 1H NMR δ (ppm): 7.57 (s, 2H), 7.21 (d, 2H), 6.86 (d, 2H), 2.84 (d, 4H), 1.71 (s, 2H), 1.34-1.29 (m, 64H), 0.89-0.85 (t, 12H). 13C NMR δ (ppm): 146.58, 140.38, 136.11, 128.00, 126.23, 125.74, 122.64, 116.91, 77.58, 77.16, 76.74, 40.19, 34.83, 33.52, 32.08, 30.13, 29.99, 29.37, 26.81, 22.85, 14.28. MS (MALDI): calculated: 1073.39, found: 1072.6 (M+). 2,6-dibromo-4,8-bis(5-(2-decyltetradecyl)thiophen-2-yl)benzo[1,2-b:4,5b']dithiophene (7). Same procedure as for 2 was used, but now 6 (0.51 g, 0.50 mmol) was used as the reactants. Yield: 0.48 g (81.2%). 1H NMR δ (ppm): 7.57 (s, 2H), 7.21 (d, 2H), 6.86 (d, 2H), 2.84 (d, 4H), 1.71 (s, 2H), 1.35-1.25 (m, 80H), 0.89-0.85 (t, 12H). 13C NMR δ (ppm): 6.59, 140.39, 136.11, 128.01, 126.23 , 125.74 , 122.64, 116.91, 77.58, 77.16, 76.74, 40.20, 34.84, 33.53, 32.08, 30.13, 29.84, 29.53 , 26.82, 22.85, 14.28. MS (MALDI): calculated: 1185.60, found: 1184.70 (M+). HD-PBDT2FT. To a degassed solution of the monomer 2 (95.12 mg, 0.099 mmol), monomer 3 (52.22 mg, 0.099 mg) in toluene (2 mL) and DMF (0.2 mL), tris(dibenzylideneacetene)dipalladium(0) (2.71 mg, 3.0 µmol) and triphenylphosphine (3.12 mg, 12 µmol) were added. The mixture was stirred at 115 °C for 16 h, after which it was precipitated in methanol and filter through a Soxhlet thimble. The polymer was extracted with acetone, hexane, dichloromethane and then dissolved in 1,1,2,2-tetrachloroethane (TCE) (80 mL) at 140 °C, which was then precipitated into acetone. Yield: 89 mg (89.8%) as a dark solid. GPC (o-DCB, 140 °C): Mn = 31.6 kg mol−1, Mw = 92.1 kg mol-1 and PDI = 2.92. OD-PBDT2FT. Same procedure as for HD-PBDT2FT was used, but now 5 (88.45 mg, 0.082 mmol) and 3 (43.50 mg, 0.082 mg) were used as the monomers. Yield: 76 mg (82.8%) as a dark solid. GPC (o-DCB, 140 °C): Mn = 77.2 kg mol−1, Mw = 144.8 kg mol-1 and PDI = 1.88.
S4
DT-PBDT2FT. Same procedure as for HD-PBDT2FT was used, but now 7 (102.97 mg, 0.087 mmol) and 3 (45.84 mg, 0.087 mol) were used as the monomers. Yield: 96 mg (90.1%) as a dark solid. GPC (o-DCB, 140 °C): Mn = 107.6 kg mol−1, Mw = 240.8 kg mol-1 and PDI = 2.24. 3. DFT calculations Density function theory (DFT) calculations were performed at the B3LYP/6-31G* level by using the Gaussian 09 program package. Table S1. DFT frontier molecular orbitals for (a) TBDT, (b) 2FT and (c) the segments of PBDT2FT.
LUMO (eV) -1.30 eV -2.40 eV
-1.33 eV
HOMO (eV) -5.59 eV -4.84 eV
-5.14 eV
Table S2. DFT frontier molecular orbitals for (a) TBDT oligmer and (b) 2FT oligomer.
LUMO (eV) -2.56 eV -2.18 eV
S5
HOMO (eV)
-4.94 eV -4.84 eV
4. GPC
Figure S1. GPC recorded at 140 °C with o-DCB as eluent for HD-, OD- and DT-PBDT2FT.
5. CV measurement S6
(a)
2.0
(b) 0.25
HD-PBDT2FT OD-PBDT2FT DT-PBDT2FT
0.20
PCBM ITIC
Current (mA)
Current (mA)
1.5 1.0 0.5
0.15 0.10 0.05
0.0 0.00
-0.5 -1.0
-0.5
0.0
0.5
1.0
-0.05 -0.5
1.5
0.0
Voltage (V)
0.5
1.0
1.5
Voltage (V)
Figure S2. Cyclic voltammogram of (a) the polymer thin films and (b) electron acceptor PCBM and ITIC thin films. Potential vs. Fc/Fc+. 6. FETs Table S3. Field effect hole mobilities of PBDT2FT in a BGBC configuration. The polymer thin films were thermally annealed (TA) for 10 min before measurement. Polymer
TA
µh
[ºC] [cm2 V-1 s-1] a
a
VT
Ion/Ioff
[V]
HD-PBDT2FT RT
0.24
-2.3
1×108
90
0.79
-2.0
1×108
120
0.32
-2.4
1×108
150
0.47
-2.4
2×108
OD-PBDT2FT RTa
0.043
-12.7
2×107
120
0.076
-14.3
9×107
150
0.091
-32.1
9×107
180
0.058
-16.0
4×104
DT-PBDT2FT RTa
0.022
-17.8
8×106
120
0.015
-16.7
7×107
150
0.015
-20.0
7×106
180
0.004
-4.2
8.8×106
Without thermal annealing.
S7
-2
10
(b)
-3
Vsd = -100 V
10
-5
-5
0.006
10
-6
-6
0.005
10
-7
10
-8
10
-9
10
-10
10
-11
10
-12
-8
10
|Isd|1/2 (A1/2)
-7
10
-9
10
0.005
10
0.004 0.003
10 0.0020
-8
10 0.0015
-9
10 0.0010
-10
10
-10
0.001
-11
10
0.000
0.000
-12
10
-100 -80 -60 -40 -20 Vg (V)
0
-0.001
20
-0.20 Vg = -100 V
-100 -80 -60 -40 -20 Vg (V)
0
0.0005 0.0000
20
-90 V
-0.004
-0.04
-80 V -70 V
Isd (mA)
-90 V
-0.03 -80 V
-0.02
-50 V
20
Vg = -100 V
Vg = -100 V
-60 V
0
(f) -0.005
-0.05
-70 V
-0.10
-12
10 -100 -80 -60 -40 -20 Vg (V)
-80 V
-0.15
-11
10
(e)
-90 V
Isd (mA)
0.0025 -7
0.002
10
(d)
-5
10
0.0030
-6
-Isd (A)
10
0.0035
(c)
Vsd = -100 V
0.007
10
0.010
-4
-4
10
0.015
10
-Isd (A)
0.020
|Isd|1/2 (A1/2)
0.008
10
|Isd|1/2 (A1/2)
Vsd = -100 V
-Isd (A)
0.025
Isd (mA)
(a)
-0.003 -60 V
-0.002 -50 V
-70 V
-0.05
0
-20
-40 -60 Vsd (V)
-40 V
-60 V -50 V
-30 V -20 - 0 V
0.00
-0.001
-0.01
-40 V
0.00
-20 V--40 V
0
-80 -100
-20
-40 -60 Vsd (V)
-40 V -80 -100
-30 V 0 V--20 V
0.000 0
-20
-40 -60 Vsd (V)
-80 -100
Figure S3. (a) – (c) Transfer and (d) – (f) output curves obtained from BGBC FET devices. (a), (d) HD-PBDT2FT thin films fabricated from o-DCB and annealed at 90 oC; (b), (d) ODPBDT2FT thin films fabricated from o-DCB and annealed at 150 oC; (c), (f) DT-PBDT2FT thin films fabricated from o-DCB without thermal annealing.
7. Solar cells of PBDT2FT:[70]PCBM The regular device configuration of ITO/PEDOT:PSS/active layer/LiF (1 nm)/Al (100 nm) was used for optimization of PBDT2FT:[70]PCBM cells. Table S4. Characteristics of HD-PBDT2FT:[70]PCBM solar cells spin coated from different solution and different ratio of donor to acceptor. Thickness
Jsca
Jscb
Voc
[nm]
[mA cm-2]
[mA cm-2]
[V]
[%]
[%]
1:1.5 CB
105
7.7
7.4
0.78 0.55
3.3
3.2
1:1.5 CB/DIO (2.5%)
80
9.8
10.1
0.79 0.58
4.5
4.6
1:1.5 CB/DIO (5%)
90
9.2
8.9
0.77 0.61
4.3
4.2
1:1
CB/DIO (2.5%)
100
8.6
8.7
0.76 0.55
3.6
3.7
1:2
CB/DIO (2.5%)
110
9.8
10.5
0.75 0.47
3.5
3.7
1:3
CB/DIO (2.5%)
90
7.9
7.9
0.74 0.54
3.5
3.5
Ratio
a
Solvent
FF PCEa PCEb
Jsc are measured under AM1.5 G spectrum from solar simulator.
integrating the EQE spectrum with the AM1.5G spectrum.
S8
b
Jsc are calculated by
Table S5. Characteristics of HD-PBDT2FT:[70]PCBM (1:1.5) solar cells spin coated from CB/DIO (2.5%) with different thickness of active layers. Jsca
Thickness [nm]
a
Jscb
Voc
PCEa PCEb
FF
[mA cm-2] [mA cm-2] [V]
[%]
[%]
50
7.9
8.2
0.78 0.65
4.0
4.2
70
8.7
9.0
0.78 0.61
4.2
4.3
80
9.8
10.1
0.79 0.58
4.5
4.6
90
9.1
9.2
0.78 0.58
4.2
4.2
110
8.7
8.8
0.78 0.56
3.8
3.8
Jsc are measured under AM1.5 G spectrum from solar simulator.
b
Jsc are calculated by
integrating the EQE spectrum with the AM1.5G spectrum. (a) 10
(b) 0.7
PBDT2FT:[70]PCBM
6
0.6
4
0.5
2
EQE
2
Current density (mA/cm )
8
0
0.4
-2
0.3
-4
0.2
PBDT2FT:[70]PCBM
-6
0.1
-8 -10 -1.0
-0.5
0.0
0.5
0.0 300
1.0
400
500
600
700
800
Wavelength (nm)
Voltage (V)
Figure S4. (a) J-V characteristics in dark (dashed lines) and under white light illumination (solid lines) and (b) EQE of the PBDT2FT:[70]PCBM (1:1.5) inverted solar cells fabricated from CB/DIO (2.5%) solution. Jsc = 9.2 mA cm-2, Voc = 0.75 V, FF = 0.59 and PCE = 3.9%. Table S6. Characteristics of OD- and DT-PBDT2FT:[70]PCBM (1:1.5) solar cells spin coated from CB with different content of additive. Thickness
Jsca
Jscb
Voc
[nm]
[mA cm-2]
[mA cm-2]
[V]
[%]
[%]
OD-PBDT2FT CB/DIO (2.5%)
80
7.2
6.9
0.74 0.57
3.0
2.9
OD-PBDT2FT CB/DIO (5%)
80
7.9
7.4
0.77 0.58
3.6
3.4
DT-PBDT2FT CB/DIO (2.5%)
80
6.8
7.0
0.79 0.59
3.1
3.2
DT-PBDT2FT CB/DIO (5%)
80
6.7
7.0
0.83 0.60
3.3
3.4
DT-PBDT2FT CB/DIO (5%)
90
6.6
6.8
0.83 0.55
3.0
3.1
DT-PBDT2FT CB/DIO (5%)
120
9.2
9.5
0.83 0.40
3.1
3.2
Polymer
a
Solvent
Jsc are measured under AM1.5 G spectrum from solar simulator.
integrating the EQE spectrum with the AM1.5G spectrum.
S9
FF
b
PCEa PCEb
Jsc are calculated by
8. Solar cells of PBDT2FT:ITIC The inverted device configuration of ITO/ZnO/active layer/MoO3 (10 nm)/Ag (100 nm) was used for optimization of PBDT2FT:ITIC cells. 10 2
Current density (mA/cm )
PBDT2FT:ITIC
5
0
-5
-10 -1.0
-0.5
0.0
0.5
1.0
1.5
Voltage (V)
Figure S5. J-V characteristics in dark (dashed lines) and under white light illumination (solid lines) regular solar cells fabricated from CB/DIO (0.2%) solution. Jsc = 8.1 mA cm-2, Voc = 0.88 V, FF = 0.33 and PCE = 2.3%. The device configuration is ITO/PEDOT:PSS/active layer/LiF/Al. Table S7. Characteristics of HD-PBDT2FT: ITIC (1:1) inverted solar cells spin coated from different solution and different ratio of donor to acceptor. Ratio
a
Solvent
Thickness
Jsca
Jscb
Voc
[nm]
[mA cm-2]
[mA cm-2]
[V]
FF
Jsca
PCEb
[mA cm-2]
[%]
1:1
CB
55
12.8
11.7
0.89 0.59
6.6
6.1
1:1
CB/DIO (0.2%)
60
14.6
14.4
0.92 0.65
8.7
8.7
1:1
CB/DIO (0.4%)
75
14.8
14.3
0.91 0.55
7.5
7.2
1:1
CB/DIO (0.6%)
55
13.5
13.5
0.92 0.59
7.3
7.3
1:0.5 CB/DIO (0.2%)
60
12.5
11.6
0.93 0.50
5.9
5.4
1:1.5 CB/DIO (0.2%)
50
12.4
12.1
0.90 0.60
6.8
6.6
Jsc are measured under AM1.5 G spectrum from solar simulator.
b
Jsc are calculated by
integrating the EQE spectrum with the AM1.5G spectrum. Table S8. Characteristics of HD-PBDT2FT:ITIC (1:1) inverted solar cells spin coated from CB/DIO (0.2%) with different thickness of active layers. Thickness [nm]
Jsca
Jscb
Voc
[mA cm-2] [mA cm-2] [V]
S10
FF
PCEa PCEb [%]
[%]
a
35
9.5
9.8
0.91 0.57
4.9
5.1
45
12.5
12.4
0.92 0.65
7.5
7.4
60
14.6
14.4
0.92 0.65
8.7
8.7
70
14.5
14.1
0.92 0.57
7.6
7.4
90
14.2
14.3
0.91 0.51
6.6
6.6
Jsc are measured under AM1.5 G spectrum from solar simulator.
b
Jsc are calculated by
integrating the EQE spectrum with the AM1.5G spectrum. Table S9. Characteristics of OD- and DT-PBDT2FT:ITIC (1:1) inverted solar cells spin coated from CB/DIO (0.2%) with different thickness of active layers. Polymer
Jscb
Voc
FF
[mA cm-2] [mA cm-2] [V]
[nm]
PCEa PCEb [%]
[%]
OD-PBDT2FT
CB
60
13.3
12.3
0.92 0.61
7.5
7.0
OD-PBDT2FT
CB/DIO (0.5%)
60
11.6
12.0
0.95 0.61
6.7
7.0
OD-PBDT2FT
CB/DIO (0.2%)
50
12.0
12.4
0.94 0.64
7.2
7.5
OD-PBDT2FT
CB/DIO (0.2%)
60
12.8
13.1
0.92 0.69
8.1
8.3
c
0.92 0.60
7.1
-c
OD-PBDT2FT
CB/DIO (0.2%)
75
13.0
-
DT-PBDT2FT
CB
60
13.2
12.6
0.95 0.55
6.9
6.6
DT-PBDT2FT
CB/DIO (0.5%)
60
11.8
11.3
0.98 0.51
5.9
5.6
DT-PBDT2FT
CB/DIO (0.2%)
50
12.9
12.4
0.96 0.59
7.2
7.0
DT-PBDT2FT
CB/DIO (0.2%)
60
13.7
13.1
0.95 0.57
7.3
7.0
DT-PBDT2FT
CB/DIO (0.2%)
70
12.2
11.7
0.96 0.56
6.6
6.3
10.9
c
0.95 0.54
5.6
-c
DT-PBDT2FT a
Jsca
Thickness
CB/DIO (0.2%)
80
-
Jsc are measured under AM1.5 G spectrum from solar simulator.
integrating the EQE spectrum with the AM1.5G spectrum.
c
b
Jsc are calculated by
The cells didn’t perform EQE
measurement. (a)
4
(b)
HD-PBDT2FT:PCBM
7
HD-PBDT2FT:ITIC
3
Number of devices
Number of devices
6
2
1
5 4 3 2 1
0 3.0
3.5
4.0
4.5
5.0
PCE (%)
0 6.5
7.0
7.5
8.0
PCE (%)
S11
8.5
9.0
9.5
(c)
6
(d)
4
OD-PBDT2FT:ITIC
OD-PBDT2FT:PCBM Number of devices
Number of devices
5 4 3 2 1 0 3.0
3.5
4.0
4.5
3
2
1
0 6.5
5.0
7.0
7.5
PCE (%)
(e)
8.0
5
(f)
Number of devices
Number of devices
4
3
2
1
3.5
4.0
9.0
9.5
4
DT-PBDT2FT:ITIC
DT-PBDT2FT:PCBM
0 3.0
8.5
PCE (%)
4.5
3
2
1
0 6.5
5.0
7.0
PCE (%)
7.5
8.0
8.5
9.0
9.5
PCE (%)
Figure S6. The PCEs distribution for at least 10 solar cells based on the polymers with PCBM or ITIC as acceptors. (a) HD-PBDT2FT:PCBM (4.3% ± 0.14). (b) HDPBDT2FT:ITIC (8.6% ± 0.20). (c) OD-PBDT2FT:PCBM (3.3% ± 0.13). (d) ODPBDT2FT:ITIC (8.0% ± 0.17). (e) DT-PBDT2FT:PCBM (3.2% ± 0.13). (f) DTPBDT2FT:ITIC (7.3% ± 0.13). The PCEs are measured under AM1.5 G spectrum from solar simulator. Table S10. Jsc calculated from EQE, IQE and average IQE. JscEQE
JscIQE -2
Average IQE -2
[mA cm ] [mA cm ] HD-PBDT2FT:PCBM
10.1
11.0
0.92
OD-PBDT2FT:PCBM
7.4
11.1
0.67
DT-PBDT2FT:PCBM
7.0
10.4
0.67
HD-PBDT2FT:ITIC
14.4
18.4
0.78
OD-PBDT2FT:ITIC
13.1
18.2
0.72
DT-PBDT2FT:ITIC
13.1
17.9
0.73
9. SCLC measurement S12
Hole mobility of the blend thin films was measured by using the device configuration of ITO/PEDOT:PSS/active layers/Au. Electron mobility of the blend thin films was measured by using the device configuration of ITO/ZnO/active layers/LiF/Al. The active layers were fabricated by using optimized condition as present in Table 2. (a)
90
(b)
HD-PBDT2FT OD-PBDT2FT DT-PBDT2FT Blend with [70]PCBM
80
80
1/2
J /A
1/2
60
1/2
HD-PBDT2FT OD-PBDT2FT DT-PBDT2FT Blended with ITIC
70
1/2
m
m
-1
-1
70
J /A
90
50
60 50
40
40
30 3.0
3.5
4.0
4.5
5.0
5.5
3.0
6.0
3.5
4.0
(c) 140 120 100
4.5
5.0
5.5
6.0
V (V)
V (V)
(d) 90
HD-PBDT2FT OD-PBDT2FT DT-PBDT2FT Blended with [70]PCBM
80 70
HD-PBDT2FT OD-PBDT2FT DT-PBDT2FT Blended With ITIC
-1
m
50
1/2
J /A
1/2
60
1/2
J /A
1/2
m
-1
60 80
40
40 30 20
20
10 0 3.0
3.5
4.0
4.5
5.0
5.5
6.0
3.0
V (V)
3.5
4.0
4.5
5.0
5.5
6.0
V (V)
Figure S7. J-V characteristics under dark for (a,b) hole-only devices and (c,d) electron-only devices. (a,c) PCBM-based cells. (b,d) ITIC-based cells. 10. TEM of PBDT2FT:ITIC
Figure S8. Bright field TEM images (1.2 × 1.2 µm2) of PBDT2FT:ITIC (1:1) thin films spin coated from CB/DIO (0.2%). (a) HD-PBDT2FT. (b) OD-PBDT2FT. (c) DT-PBDT2FT. 11. NMR spectra of the monomers and polymers
S13
Figure S9. 1H-NMR of the monomer 2 recorded in CDCl3.
Figure S10. 13C-NMR of the monomer 2 recorded in CDCl3.
Figure S11. 1H-NMR of the monomer 5 recorded in CDCl3. S14
Figure S12. 13C-NMR of the monomer 5 recorded in CDCl3.
Figure S13. 1H-NMR of the monomer 7 recorded in CDCl3.
Figure S14. 13C-NMR of the monomer 7 recorded in CDCl3.
S15
Figure S15. 1H-NMR of the polymer HD-PBDT2FT recorded at 100 ºC with 1,1,2,2tetrachloroethane-d2 as the solvent.
Figure S16. 1H-NMR of the polymer OD-PBDT2FT recorded at 100 ºC with 1,1,2,2tetrachloroethane-d2 as the solvent.
S16
Figure S17. 1H-NMR of the polymer DT-PBDT2FT recorded at 100 ºC with 1,1,2,2tetrachloroethane-d2 as the solvent. 12. References (S1) Zhou, J.; Zuo, Y.; Wan, X.; Long, G.; Zhang, Q.; Ni, W.; Liu, Y.; Li, Z.; He, G.; Li, C.; Kan, B.; Li, M.; Chen, Y. Solution-Processed and High-Performance Organic Solar Cells Using Small Molecules with a Benzodithiophene Unit. J. Am. Chem. Soc. 2013, 135, 8484-8487. (S2)
Kim, J.; Young Shim, J.; Lee, J.; Yong Lee, D.; Chae, S.; Kim, J.; Kim, I.; Jung Kim, H.; Heum Park, S.; Suh, H. Syntheses of Pyrimidine-based Polymers Containing Electron-Withdrawing Substituent with High Open Circuit Voltage and Applications for Polymer Solar Cells. J. Polym. Sci. Part A: Polym. Chem. 2016, 54, 771-784.
(S3)
Liu, Y.; Wang, H.; Dong, H.; Tan, J.; Hu, W.; Zhan, X. Synthesis of a Conjugated Polymer with Broad Absorption and Its Application in High-Performance Phototransistors. Macromolecules 2012, 45, 1296-1302.
(S4) Alexander, H.; Wim, B.; James, G.; Eric, S.; Eliot, G.; Rick, K.; Alastair, M.; Matthew, C.; Bruce, R.; Howard, P. A SAXS/WAXS/GISAXS Beamline with Multilayer Monochromator. J. Phys. Conf. Ser. 2010, 247, 012007. (S5) Gann, E.; Young, A. T.; Collins, B. A.; Yan, H.; Nasiatka, J.; Padmore, H. A.; Ade, H.; Hexemer, A.; Wang, C. Soft x-ray Scattering Facility at the Advanced Light Source with Real-Time Data Processing and Analysis. Rew. Sci. Instru. 2012, 83, 045110.
S17
(S6)
Sun, Y. M.; Seo, J. H.; Takacs, C. J.; Seifter, J.; Heeger, A. J. Inverted Polymer Solar Cells Integrated with a Low-Temperature-Annealed Sol-Gel-Derived ZnO Film as an Electron Transport Layer. Adv. Mater. 2011, 23, 1679-1683.
(S7)
Pettersson, L. A. A.; Roman, L. S.; Inganäs, O. Modeling Photocurrent Action Spectra of Photovoltaic Devices Based on Organic Thin Films. J. Appl. Phys. 1999, 86, 487496.
(S8) Burkhard, G. F.; Hoke, E. T.; McGehee, M. D. Accounting for Interference, Scattering, and Electrode Absorption to Make Accurate Internal Quantum Efficiency Measurements in Organic and Other Thin Solar Cells. Adv. Mater. 2010, 22, 32933297.
S18
Effect of Alkyl Side Chains of Conjugated Polymer Donors on the Device Performance of Non-Fullerene Solar Cells Dongdong Xia,† Yang Wu,‡ Qiang Wang,§ Andong Zhang,† Cheng Li,*, † Yuze Lin,⊥ Fallon J. M. Colberts,§ Jacobus J. van Franeker,§ René A. J. Janssen,§ Xiaowei Zhan,⊥ Wenping Hu,† Zheng Tang,*,║ Wei Ma*,‡ and Weiwei Li*,† †
Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 10090, China. Email: [email protected], [email protected]
‡
State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, PR China. E-mail: [email protected]
§
Molecular Materials and Nanosystems & Institute for Complex Molecular Systems, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
⊥
Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, China.
║
Institut für Angewandte Photophysik, Technische Universität Dresden, George-BährStraße 1, 01069, Dresden, Germany. E-mail: [email protected]
S0
Contents 1.
Materials and measurements
2.
Synthesis of the monomers and polymers
3.
DFT calculations
4.
GPC
5.
CV measurement
6.
FETs
7.
Solar cells of PBDT2FT:[70]PCBM
8.
Solar cells of PBDT2FT:ITIC
9.
SCLC measurement
10.
TEM of PBDT2FT:ITIC
11.
NMR spectra of the monomers and polymers
12.
References
1. Materials and measurements All synthetic procedures were performed under argon atmosphere. Commercial chemicals were used as received. THF and toluene were distilled from sodium under an N2 atmosphere. [6,6]-phenyl-C71-butyric acid methyl ester ([70]PCBM) and the electron acceptor ITIC were purchased from Solarmer Materials Inc. (3,3'-difluoro-[2,2'-bithiophene]-5,5'diyl)bis(trimethylstannane)
(3)
was
purchased
from
SunaTech
hexyldecyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene (1),S
1
Inc.
4,8-bis(5-(2-
4,8-bis(5-(2-octyldodecyl)-
thiophen-2-yl)benzo[1,2-b:4,5-b']dithiopheneS 2 and 4,8-bis(5-(2-decyltetradecyl)thiophen-2yl)benzo[1,2-b:4,5-b']dithiopheneS3 were synthesized according to literature procedures. 1HNMR and 13C-NMR spectra were recorded at 400 MHz and 100 MHz on a Bruker AVANCE spectrometer with CDCl3 as the solvent and tetramethylsilane (TMS) as the internal standard. Molecular weight was determined with GPC at 140 °C on a PL-GPC 220 system using a PLGEL 10 µm MIXED-B column and o-DCB as the eluent against polystyrene standards. Low concentration of 0.1 mg mL-1 polymer in o-DCB was applied to reduce aggregation. Optical absorption spectra were recorded on a JASCO V-570 spectrometer with a slit width of 2.0 nm and a scan speed of 1000 nm min-1. Cyclic voltammetry was performed under an inert atmosphere at a scan rate of 0.1 V s-1 and 1 M tetrabutylammonium hexafluorophosphate in acetonitrile as the electrolyte, a glassy-carbon working electrode coated with samples, a platinum-wire auxiliary electrode, and an Ag/AgCl as a reference electrode.
S1
TEM was performed on a Tecnai G2 Sphera transmission electron microscope (FEI) operated at 200 kV on films floated from PEDOT:PSS coated substrates in deionized water. GIWAXS measurements were performed at beamline 7.3.3S4 at the Advanced Light Source. Samples were prepared on Si substrates using identical blend solutions as those used in devices. The 10 keV X-ray beam was incident at a grazing angle of 0.12°-0.16°, selected to maximize the scattering intensity from the samples. The scattered x-rays were detected using a Dectris Pilatus 2M photon counting detector. R-SoXS transmission measurements were performed at beamline 11.0.1.2S 5 at the Advanced Light Source (ALS). Samples for R-SoXS measurements were prepared on a PEDOT:PSS modified Si substrate under the same conditions as those used for device fabrication, and then transferred by floating in water to a 1.5 mm × 1.5 mm, 100 nm thick Si3N4 membrane supported by a 5 mm × 5 mm, 200 µm thick Si frame (Norcada Inc.). 2-D scattering patterns were collected on an in-vacuum CCD camera (Princeton Instrument PIMTE). The sample detector distance was calibrated from diffraction peaks of a triblock copolymer poly(isoprene-b-styrene-b-2-vinyl pyridine), which has a known spacing of 391 Å. The beam size at the sample is approximately 100 µm by 200 µm. The organic field-effect transistors were fabricated on a commercial Si/SiO2/Au substrate purchased from First MEMS Co. Ltd. A heavily N-doped Si wafer with a SiO2 layer of 300 nm served as the gate electrode and dielectric layer, respectively. The Ti (2 nm)/Au (28 nm) source−drain electrodes were sputtered and patterned by a lift-off technique. Before deposition of the organic semiconductor, the gate dielectrics were treated with octadecyltrichlorosilane (OTS) in a vacuum oven at a temperature of 120 °C, forming an OTS self-assembled monolayers. The treated substrates were rinsed successively with hexane, chloroform, and isopropyl alcohol. Polymer thin films were spin coated on the substrate from o-DCB solution with a thickness of around 30 – 50 nm. The devices were thermally annealed at certain temperature for 10 min in a glovebox filled with N2 before measurement. The devices were measured on a Keithley 4200 SCS semiconductor parameter analyzer at room temperature. The mobilities were calculated from the saturation region with the following equation: ISD = (W/2L)Ciµ(VG-VT)2, where ISD is the drain–source current, W is the channel width (1400 µm), L is the channel length (50 µm), µ is the field-effect mobility, Ci is the capacitance per unit area of the gate dielectric layer, and VG and VT are the gate voltage and threshold voltage, respectively. This equation defines the important characteristics of electron mobility (µ), on/off ratio (Ion/Ioff), and threshold voltage (VT), which could be deduced by the equation from the plot of current–voltage. S2
Photovoltaic devices with inverted configuration were made by spin-coating a ZnO solS6
gel at 4000 rpm for 60 s onto pre-cleaned, patterned ITO substrates. The photoactive layer was deposited by spin coating a chlorobenzene solution containing PBDT2FT and [70]PCBM (or ITIC) and the appropriate amount of DIO as processing additive in air. MoO3 (10 nm) and Ag (100 nm) were deposited by vacuum evaporation at ca. 4 × 10-5 Pa as the back electrode. For the regular device configuration, poly(ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) (Clevios P, VP AI 4083) was spin coated onto ITO substrates, following by spin coating active layers. LiF (1 nm) and Al (100 nm) were deposited by vacuum evaporation as back electrode. The active area of the cells was 0.04 cm2. The J-V characteristics were measured by a Keithley 2400 source meter unit under AM1.5G spectrum from a solar simulator (Enlitech model SS-F5-3A). Solar simulator illumination intensity was determined at 100 mW cm−2 using a monocrystal silicon reference cell with KG5 filter. Short circuit currents under AM1.5G conditions were estimated from the spectral response and convolution with the solar spectrum. The external quantum efficiency was measured by a Solar Cell Spectral Response Measurement System QE-R3011 (Enli Technology Co., Ltd.). The thickness of the active layers in the photovoltaic devices was measured on a Veeco Dektak XT profilometer. Calculation of the IQE spectra was done by taking the ratio between the measured EQE and the theoretical maximum EQE predicted by a transfer matrix model.S 7 Extinction coefficients of the active materials systems were measured by using the Beer-lambert Law, with reflection and transmission of thin film samples (deposited on glass) measured by an integrating sphere. Refractive indices were simply assumed to be 2 according to reference.S8 For modeling the theoretical maximum EQE, we used a 80 nm thick active layer for the PCBM based solar cells with a regular device structure, and a 60 nm thick active layer for the ITIC solar cells with an inverted geometry. 2. Synthesis of the monomers and polymers 2,6-dibromo-4,8-bis(5-(2-hexyldecyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene (2). n-BuLi (2.4 M hexane solution, 5.9 mL, 2.47 mmol) was added dropwise into a solution of compound 1 (0.66 g, 0.82 mmol) in 10 ml dry THF at room temperature (RT). The mixture was maintained at this temperature for 3 h. After cooled to -78 ºC, CBr4 (1.09 g, 3.29 mmol) in anhydrous THF (5 mL) was added dropwise and the mixture was stirred for another 30 min. After warmed to room temperature overnight, the mixture was poured into water (100 mL), extracted with diethyl ether (100 mL), washed with brine and dried over MgSO4. After S3
removal of the solvent, the residue was purified by silica gel chromatography (hexane) to afford compound 2 (0.48 g, 60.8%) as a yellow oil. 1H NMR δ (ppm): 7.57 (s, 2H), 7.21 (d, 2H), 6.86 (d, 2H), 2.84 (d, 4H), 1.71 (m, 2H), 1.42-1.29 (m, 48H), 0.89-0.85 (t, 12H).
13
C
NMR δ (ppm): 146.6, 140.4, 136.1, 136.1, 128.0, 126.2, 125.7, 122.6, 116.9, 40.2, 34.8, 33.5, 32.08, 32.05, 30.1, 29.81, 29.79, 29.5, 26.81, 26.80, 22.9, 14.3. MS (MALDI): calculated: 958.29, found: 960.1 (M+). 2,6-dibromo-4,8-bis(5-(2-octyldodecyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene (5). Same procedure as for 2 was used, but now 4 (0.51 g, 0.56 mmol) was used as the reactants. Yield: 0.42 g (70.3%). 1H NMR δ (ppm): 7.57 (s, 2H), 7.21 (d, 2H), 6.86 (d, 2H), 2.84 (d, 4H), 1.71 (s, 2H), 1.34-1.29 (m, 64H), 0.89-0.85 (t, 12H). 13C NMR δ (ppm): 146.58, 140.38, 136.11, 128.00, 126.23, 125.74, 122.64, 116.91, 77.58, 77.16, 76.74, 40.19, 34.83, 33.52, 32.08, 30.13, 29.99, 29.37, 26.81, 22.85, 14.28. MS (MALDI): calculated: 1073.39, found: 1072.6 (M+). 2,6-dibromo-4,8-bis(5-(2-decyltetradecyl)thiophen-2-yl)benzo[1,2-b:4,5b']dithiophene (7). Same procedure as for 2 was used, but now 6 (0.51 g, 0.50 mmol) was used as the reactants. Yield: 0.48 g (81.2%). 1H NMR δ (ppm): 7.57 (s, 2H), 7.21 (d, 2H), 6.86 (d, 2H), 2.84 (d, 4H), 1.71 (s, 2H), 1.35-1.25 (m, 80H), 0.89-0.85 (t, 12H). 13C NMR δ (ppm): 6.59, 140.39, 136.11, 128.01, 126.23 , 125.74 , 122.64, 116.91, 77.58, 77.16, 76.74, 40.20, 34.84, 33.53, 32.08, 30.13, 29.84, 29.53 , 26.82, 22.85, 14.28. MS (MALDI): calculated: 1185.60, found: 1184.70 (M+). HD-PBDT2FT. To a degassed solution of the monomer 2 (95.12 mg, 0.099 mmol), monomer 3 (52.22 mg, 0.099 mg) in toluene (2 mL) and DMF (0.2 mL), tris(dibenzylideneacetene)dipalladium(0) (2.71 mg, 3.0 µmol) and triphenylphosphine (3.12 mg, 12 µmol) were added. The mixture was stirred at 115 °C for 16 h, after which it was precipitated in methanol and filter through a Soxhlet thimble. The polymer was extracted with acetone, hexane, dichloromethane and then dissolved in 1,1,2,2-tetrachloroethane (TCE) (80 mL) at 140 °C, which was then precipitated into acetone. Yield: 89 mg (89.8%) as a dark solid. GPC (o-DCB, 140 °C): Mn = 31.6 kg mol−1, Mw = 92.1 kg mol-1 and PDI = 2.92. OD-PBDT2FT. Same procedure as for HD-PBDT2FT was used, but now 5 (88.45 mg, 0.082 mmol) and 3 (43.50 mg, 0.082 mg) were used as the monomers. Yield: 76 mg (82.8%) as a dark solid. GPC (o-DCB, 140 °C): Mn = 77.2 kg mol−1, Mw = 144.8 kg mol-1 and PDI = 1.88.
S4
DT-PBDT2FT. Same procedure as for HD-PBDT2FT was used, but now 7 (102.97 mg, 0.087 mmol) and 3 (45.84 mg, 0.087 mol) were used as the monomers. Yield: 96 mg (90.1%) as a dark solid. GPC (o-DCB, 140 °C): Mn = 107.6 kg mol−1, Mw = 240.8 kg mol-1 and PDI = 2.24. 3. DFT calculations Density function theory (DFT) calculations were performed at the B3LYP/6-31G* level by using the Gaussian 09 program package. Table S1. DFT frontier molecular orbitals for (a) TBDT, (b) 2FT and (c) the segments of PBDT2FT.
LUMO (eV) -1.30 eV -2.40 eV
-1.33 eV
HOMO (eV) -5.59 eV -4.84 eV
-5.14 eV
Table S2. DFT frontier molecular orbitals for (a) TBDT oligmer and (b) 2FT oligomer.
LUMO (eV) -2.56 eV -2.18 eV
S5
HOMO (eV)
-4.94 eV -4.84 eV
4. GPC
Figure S1. GPC recorded at 140 °C with o-DCB as eluent for HD-, OD- and DT-PBDT2FT.
5. CV measurement S6
(a)
2.0
(b) 0.25
HD-PBDT2FT OD-PBDT2FT DT-PBDT2FT
0.20
PCBM ITIC
Current (mA)
Current (mA)
1.5 1.0 0.5
0.15 0.10 0.05
0.0 0.00
-0.5 -1.0
-0.5
0.0
0.5
1.0
-0.05 -0.5
1.5
0.0
Voltage (V)
0.5
1.0
1.5
Voltage (V)
Figure S2. Cyclic voltammogram of (a) the polymer thin films and (b) electron acceptor PCBM and ITIC thin films. Potential vs. Fc/Fc+. 6. FETs Table S3. Field effect hole mobilities of PBDT2FT in a BGBC configuration. The polymer thin films were thermally annealed (TA) for 10 min before measurement. Polymer
TA
µh
[ºC] [cm2 V-1 s-1] a
a
VT
Ion/Ioff
[V]
HD-PBDT2FT RT
0.24
-2.3
1×108
90
0.79
-2.0
1×108
120
0.32
-2.4
1×108
150
0.47
-2.4
2×108
OD-PBDT2FT RTa
0.043
-12.7
2×107
120
0.076
-14.3
9×107
150
0.091
-32.1
9×107
180
0.058
-16.0
4×104
DT-PBDT2FT RTa
0.022
-17.8
8×106
120
0.015
-16.7
7×107
150
0.015
-20.0
7×106
180
0.004
-4.2
8.8×106
Without thermal annealing.
S7
-2
10
(b)
-3
Vsd = -100 V
10
-5
-5
0.006
10
-6
-6
0.005
10
-7
10
-8
10
-9
10
-10
10
-11
10
-12
-8
10
|Isd|1/2 (A1/2)
-7
10
-9
10
0.005
10
0.004 0.003
10 0.0020
-8
10 0.0015
-9
10 0.0010
-10
10
-10
0.001
-11
10
0.000
0.000
-12
10
-100 -80 -60 -40 -20 Vg (V)
0
-0.001
20
-0.20 Vg = -100 V
-100 -80 -60 -40 -20 Vg (V)
0
0.0005 0.0000
20
-90 V
-0.004
-0.04
-80 V -70 V
Isd (mA)
-90 V
-0.03 -80 V
-0.02
-50 V
20
Vg = -100 V
Vg = -100 V
-60 V
0
(f) -0.005
-0.05
-70 V
-0.10
-12
10 -100 -80 -60 -40 -20 Vg (V)
-80 V
-0.15
-11
10
(e)
-90 V
Isd (mA)
0.0025 -7
0.002
10
(d)
-5
10
0.0030
-6
-Isd (A)
10
0.0035
(c)
Vsd = -100 V
0.007
10
0.010
-4
-4
10
0.015
10
-Isd (A)
0.020
|Isd|1/2 (A1/2)
0.008
10
|Isd|1/2 (A1/2)
Vsd = -100 V
-Isd (A)
0.025
Isd (mA)
(a)
-0.003 -60 V
-0.002 -50 V
-70 V
-0.05
0
-20
-40 -60 Vsd (V)
-40 V
-60 V -50 V
-30 V -20 - 0 V
0.00
-0.001
-0.01
-40 V
0.00
-20 V--40 V
0
-80 -100
-20
-40 -60 Vsd (V)
-40 V -80 -100
-30 V 0 V--20 V
0.000 0
-20
-40 -60 Vsd (V)
-80 -100
Figure S3. (a) – (c) Transfer and (d) – (f) output curves obtained from BGBC FET devices. (a), (d) HD-PBDT2FT thin films fabricated from o-DCB and annealed at 90 oC; (b), (d) ODPBDT2FT thin films fabricated from o-DCB and annealed at 150 oC; (c), (f) DT-PBDT2FT thin films fabricated from o-DCB without thermal annealing.
7. Solar cells of PBDT2FT:[70]PCBM The regular device configuration of ITO/PEDOT:PSS/active layer/LiF (1 nm)/Al (100 nm) was used for optimization of PBDT2FT:[70]PCBM cells. Table S4. Characteristics of HD-PBDT2FT:[70]PCBM solar cells spin coated from different solution and different ratio of donor to acceptor. Thickness
Jsca
Jscb
Voc
[nm]
[mA cm-2]
[mA cm-2]
[V]
[%]
[%]
1:1.5 CB
105
7.7
7.4
0.78 0.55
3.3
3.2
1:1.5 CB/DIO (2.5%)
80
9.8
10.1
0.79 0.58
4.5
4.6
1:1.5 CB/DIO (5%)
90
9.2
8.9
0.77 0.61
4.3
4.2
1:1
CB/DIO (2.5%)
100
8.6
8.7
0.76 0.55
3.6
3.7
1:2
CB/DIO (2.5%)
110
9.8
10.5
0.75 0.47
3.5
3.7
1:3
CB/DIO (2.5%)
90
7.9
7.9
0.74 0.54
3.5
3.5
Ratio
a
Solvent
FF PCEa PCEb
Jsc are measured under AM1.5 G spectrum from solar simulator.
integrating the EQE spectrum with the AM1.5G spectrum.
S8
b
Jsc are calculated by
Table S5. Characteristics of HD-PBDT2FT:[70]PCBM (1:1.5) solar cells spin coated from CB/DIO (2.5%) with different thickness of active layers. Jsca
Thickness [nm]
a
Jscb
Voc
PCEa PCEb
FF
[mA cm-2] [mA cm-2] [V]
[%]
[%]
50
7.9
8.2
0.78 0.65
4.0
4.2
70
8.7
9.0
0.78 0.61
4.2
4.3
80
9.8
10.1
0.79 0.58
4.5
4.6
90
9.1
9.2
0.78 0.58
4.2
4.2
110
8.7
8.8
0.78 0.56
3.8
3.8
Jsc are measured under AM1.5 G spectrum from solar simulator.
b
Jsc are calculated by
integrating the EQE spectrum with the AM1.5G spectrum. (a) 10
(b) 0.7
PBDT2FT:[70]PCBM
6
0.6
4
0.5
2
EQE
2
Current density (mA/cm )
8
0
0.4
-2
0.3
-4
0.2
PBDT2FT:[70]PCBM
-6
0.1
-8 -10 -1.0
-0.5
0.0
0.5
0.0 300
1.0
400
500
600
700
800
Wavelength (nm)
Voltage (V)
Figure S4. (a) J-V characteristics in dark (dashed lines) and under white light illumination (solid lines) and (b) EQE of the PBDT2FT:[70]PCBM (1:1.5) inverted solar cells fabricated from CB/DIO (2.5%) solution. Jsc = 9.2 mA cm-2, Voc = 0.75 V, FF = 0.59 and PCE = 3.9%. Table S6. Characteristics of OD- and DT-PBDT2FT:[70]PCBM (1:1.5) solar cells spin coated from CB with different content of additive. Thickness
Jsca
Jscb
Voc
[nm]
[mA cm-2]
[mA cm-2]
[V]
[%]
[%]
OD-PBDT2FT CB/DIO (2.5%)
80
7.2
6.9
0.74 0.57
3.0
2.9
OD-PBDT2FT CB/DIO (5%)
80
7.9
7.4
0.77 0.58
3.6
3.4
DT-PBDT2FT CB/DIO (2.5%)
80
6.8
7.0
0.79 0.59
3.1
3.2
DT-PBDT2FT CB/DIO (5%)
80
6.7
7.0
0.83 0.60
3.3
3.4
DT-PBDT2FT CB/DIO (5%)
90
6.6
6.8
0.83 0.55
3.0
3.1
DT-PBDT2FT CB/DIO (5%)
120
9.2
9.5
0.83 0.40
3.1
3.2
Polymer
a
Solvent
Jsc are measured under AM1.5 G spectrum from solar simulator.
integrating the EQE spectrum with the AM1.5G spectrum.
S9
FF
b
PCEa PCEb
Jsc are calculated by
8. Solar cells of PBDT2FT:ITIC The inverted device configuration of ITO/ZnO/active layer/MoO3 (10 nm)/Ag (100 nm) was used for optimization of PBDT2FT:ITIC cells. 10 2
Current density (mA/cm )
PBDT2FT:ITIC
5
0
-5
-10 -1.0
-0.5
0.0
0.5
1.0
1.5
Voltage (V)
Figure S5. J-V characteristics in dark (dashed lines) and under white light illumination (solid lines) regular solar cells fabricated from CB/DIO (0.2%) solution. Jsc = 8.1 mA cm-2, Voc = 0.88 V, FF = 0.33 and PCE = 2.3%. The device configuration is ITO/PEDOT:PSS/active layer/LiF/Al. Table S7. Characteristics of HD-PBDT2FT: ITIC (1:1) inverted solar cells spin coated from different solution and different ratio of donor to acceptor. Ratio
a
Solvent
Thickness
Jsca
Jscb
Voc
[nm]
[mA cm-2]
[mA cm-2]
[V]
FF
Jsca
PCEb
[mA cm-2]
[%]
1:1
CB
55
12.8
11.7
0.89 0.59
6.6
6.1
1:1
CB/DIO (0.2%)
60
14.6
14.4
0.92 0.65
8.7
8.7
1:1
CB/DIO (0.4%)
75
14.8
14.3
0.91 0.55
7.5
7.2
1:1
CB/DIO (0.6%)
55
13.5
13.5
0.92 0.59
7.3
7.3
1:0.5 CB/DIO (0.2%)
60
12.5
11.6
0.93 0.50
5.9
5.4
1:1.5 CB/DIO (0.2%)
50
12.4
12.1
0.90 0.60
6.8
6.6
Jsc are measured under AM1.5 G spectrum from solar simulator.
b
Jsc are calculated by
integrating the EQE spectrum with the AM1.5G spectrum. Table S8. Characteristics of HD-PBDT2FT:ITIC (1:1) inverted solar cells spin coated from CB/DIO (0.2%) with different thickness of active layers. Thickness [nm]
Jsca
Jscb
Voc
[mA cm-2] [mA cm-2] [V]
S10
FF
PCEa PCEb [%]
[%]
a
35
9.5
9.8
0.91 0.57
4.9
5.1
45
12.5
12.4
0.92 0.65
7.5
7.4
60
14.6
14.4
0.92 0.65
8.7
8.7
70
14.5
14.1
0.92 0.57
7.6
7.4
90
14.2
14.3
0.91 0.51
6.6
6.6
Jsc are measured under AM1.5 G spectrum from solar simulator.
b
Jsc are calculated by
integrating the EQE spectrum with the AM1.5G spectrum. Table S9. Characteristics of OD- and DT-PBDT2FT:ITIC (1:1) inverted solar cells spin coated from CB/DIO (0.2%) with different thickness of active layers. Polymer
Jscb
Voc
FF
[mA cm-2] [mA cm-2] [V]
[nm]
PCEa PCEb [%]
[%]
OD-PBDT2FT
CB
60
13.3
12.3
0.92 0.61
7.5
7.0
OD-PBDT2FT
CB/DIO (0.5%)
60
11.6
12.0
0.95 0.61
6.7
7.0
OD-PBDT2FT
CB/DIO (0.2%)
50
12.0
12.4
0.94 0.64
7.2
7.5
OD-PBDT2FT
CB/DIO (0.2%)
60
12.8
13.1
0.92 0.69
8.1
8.3
c
0.92 0.60
7.1
-c
OD-PBDT2FT
CB/DIO (0.2%)
75
13.0
-
DT-PBDT2FT
CB
60
13.2
12.6
0.95 0.55
6.9
6.6
DT-PBDT2FT
CB/DIO (0.5%)
60
11.8
11.3
0.98 0.51
5.9
5.6
DT-PBDT2FT
CB/DIO (0.2%)
50
12.9
12.4
0.96 0.59
7.2
7.0
DT-PBDT2FT
CB/DIO (0.2%)
60
13.7
13.1
0.95 0.57
7.3
7.0
DT-PBDT2FT
CB/DIO (0.2%)
70
12.2
11.7
0.96 0.56
6.6
6.3
10.9
c
0.95 0.54
5.6
-c
DT-PBDT2FT a
Jsca
Thickness
CB/DIO (0.2%)
80
-
Jsc are measured under AM1.5 G spectrum from solar simulator.
integrating the EQE spectrum with the AM1.5G spectrum.
c
b
Jsc are calculated by
The cells didn’t perform EQE
measurement. (a)
4
(b)
HD-PBDT2FT:PCBM
7
HD-PBDT2FT:ITIC
3
Number of devices
Number of devices
6
2
1
5 4 3 2 1
0 3.0
3.5
4.0
4.5
5.0
PCE (%)
0 6.5
7.0
7.5
8.0
PCE (%)
S11
8.5
9.0
9.5
(c)
6
(d)
4
OD-PBDT2FT:ITIC
OD-PBDT2FT:PCBM Number of devices
Number of devices
5 4 3 2 1 0 3.0
3.5
4.0
4.5
3
2
1
0 6.5
5.0
7.0
7.5
PCE (%)
(e)
8.0
5
(f)
Number of devices
Number of devices
4
3
2
1
3.5
4.0
9.0
9.5
4
DT-PBDT2FT:ITIC
DT-PBDT2FT:PCBM
0 3.0
8.5
PCE (%)
4.5
3
2
1
0 6.5
5.0
7.0
PCE (%)
7.5
8.0
8.5
9.0
9.5
PCE (%)
Figure S6. The PCEs distribution for at least 10 solar cells based on the polymers with PCBM or ITIC as acceptors. (a) HD-PBDT2FT:PCBM (4.3% ± 0.14). (b) HDPBDT2FT:ITIC (8.6% ± 0.20). (c) OD-PBDT2FT:PCBM (3.3% ± 0.13). (d) ODPBDT2FT:ITIC (8.0% ± 0.17). (e) DT-PBDT2FT:PCBM (3.2% ± 0.13). (f) DTPBDT2FT:ITIC (7.3% ± 0.13). The PCEs are measured under AM1.5 G spectrum from solar simulator. Table S10. Jsc calculated from EQE, IQE and average IQE. JscEQE
JscIQE -2
Average IQE -2
[mA cm ] [mA cm ] HD-PBDT2FT:PCBM
10.1
11.0
0.92
OD-PBDT2FT:PCBM
7.4
11.1
0.67
DT-PBDT2FT:PCBM
7.0
10.4
0.67
HD-PBDT2FT:ITIC
14.4
18.4
0.78
OD-PBDT2FT:ITIC
13.1
18.2
0.72
DT-PBDT2FT:ITIC
13.1
17.9
0.73
9. SCLC measurement S12
Hole mobility of the blend thin films was measured by using the device configuration of ITO/PEDOT:PSS/active layers/Au. Electron mobility of the blend thin films was measured by using the device configuration of ITO/ZnO/active layers/LiF/Al. The active layers were fabricated by using optimized condition as present in Table 2. (a)
90
(b)
HD-PBDT2FT OD-PBDT2FT DT-PBDT2FT Blend with [70]PCBM
80
80
1/2
J /A
1/2
60
1/2
HD-PBDT2FT OD-PBDT2FT DT-PBDT2FT Blended with ITIC
70
1/2
m
m
-1
-1
70
J /A
90
50
60 50
40
40
30 3.0
3.5
4.0
4.5
5.0
5.5
3.0
6.0
3.5
4.0
(c) 140 120 100
4.5
5.0
5.5
6.0
V (V)
V (V)
(d) 90
HD-PBDT2FT OD-PBDT2FT DT-PBDT2FT Blended with [70]PCBM
80 70
HD-PBDT2FT OD-PBDT2FT DT-PBDT2FT Blended With ITIC
-1
m
50
1/2
J /A
1/2
60
1/2
J /A
1/2
m
-1
60 80
40
40 30 20
20
10 0 3.0
3.5
4.0
4.5
5.0
5.5
6.0
3.0
V (V)
3.5
4.0
4.5
5.0
5.5
6.0
V (V)
Figure S7. J-V characteristics under dark for (a,b) hole-only devices and (c,d) electron-only devices. (a,c) PCBM-based cells. (b,d) ITIC-based cells. 10. TEM of PBDT2FT:ITIC
Figure S8. Bright field TEM images (1.2 × 1.2 µm2) of PBDT2FT:ITIC (1:1) thin films spin coated from CB/DIO (0.2%). (a) HD-PBDT2FT. (b) OD-PBDT2FT. (c) DT-PBDT2FT. 11. NMR spectra of the monomers and polymers
S13
Figure S9. 1H-NMR of the monomer 2 recorded in CDCl3.
Figure S10. 13C-NMR of the monomer 2 recorded in CDCl3.
Figure S11. 1H-NMR of the monomer 5 recorded in CDCl3. S14
Figure S12. 13C-NMR of the monomer 5 recorded in CDCl3.
Figure S13. 1H-NMR of the monomer 7 recorded in CDCl3.
Figure S14. 13C-NMR of the monomer 7 recorded in CDCl3.
S15
Figure S15. 1H-NMR of the polymer HD-PBDT2FT recorded at 100 ºC with 1,1,2,2tetrachloroethane-d2 as the solvent.
Figure S16. 1H-NMR of the polymer OD-PBDT2FT recorded at 100 ºC with 1,1,2,2tetrachloroethane-d2 as the solvent.
S16
Figure S17. 1H-NMR of the polymer DT-PBDT2FT recorded at 100 ºC with 1,1,2,2tetrachloroethane-d2 as the solvent. 12. References (S1) Zhou, J.; Zuo, Y.; Wan, X.; Long, G.; Zhang, Q.; Ni, W.; Liu, Y.; Li, Z.; He, G.; Li, C.; Kan, B.; Li, M.; Chen, Y. Solution-Processed and High-Performance Organic Solar Cells Using Small Molecules with a Benzodithiophene Unit. J. Am. Chem. Soc. 2013, 135, 8484-8487. (S2)
Kim, J.; Young Shim, J.; Lee, J.; Yong Lee, D.; Chae, S.; Kim, J.; Kim, I.; Jung Kim, H.; Heum Park, S.; Suh, H. Syntheses of Pyrimidine-based Polymers Containing Electron-Withdrawing Substituent with High Open Circuit Voltage and Applications for Polymer Solar Cells. J. Polym. Sci. Part A: Polym. Chem. 2016, 54, 771-784.
(S3)
Liu, Y.; Wang, H.; Dong, H.; Tan, J.; Hu, W.; Zhan, X. Synthesis of a Conjugated Polymer with Broad Absorption and Its Application in High-Performance Phototransistors. Macromolecules 2012, 45, 1296-1302.
(S4) Alexander, H.; Wim, B.; James, G.; Eric, S.; Eliot, G.; Rick, K.; Alastair, M.; Matthew, C.; Bruce, R.; Howard, P. A SAXS/WAXS/GISAXS Beamline with Multilayer Monochromator. J. Phys. Conf. Ser. 2010, 247, 012007. (S5) Gann, E.; Young, A. T.; Collins, B. A.; Yan, H.; Nasiatka, J.; Padmore, H. A.; Ade, H.; Hexemer, A.; Wang, C. Soft x-ray Scattering Facility at the Advanced Light Source with Real-Time Data Processing and Analysis. Rew. Sci. Instru. 2012, 83, 045110.
S17
(S6)
Sun, Y. M.; Seo, J. H.; Takacs, C. J.; Seifter, J.; Heeger, A. J. Inverted Polymer Solar Cells Integrated with a Low-Temperature-Annealed Sol-Gel-Derived ZnO Film as an Electron Transport Layer. Adv. Mater. 2011, 23, 1679-1683.
(S7)
Pettersson, L. A. A.; Roman, L. S.; Inganäs, O. Modeling Photocurrent Action Spectra of Photovoltaic Devices Based on Organic Thin Films. J. Appl. Phys. 1999, 86, 487496.
(S8) Burkhard, G. F.; Hoke, E. T.; McGehee, M. D. Accounting for Interference, Scattering, and Electrode Absorption to Make Accurate Internal Quantum Efficiency Measurements in Organic and Other Thin Solar Cells. Adv. Mater. 2010, 22, 32933297.
S18
