Yan Liu, Gongchu Liu, Ruihao Xie, Zhenfeng Wang, Wenkai Zhong, Yuan Li*, Fei

Transcription

1 Supporting Information A rational design and synthesis of cross-conjugated small molecule acceptors approaching high performance fullerene-free polymer solar cells Yan Liu, Gongchu Liu, Ruihao Xie, Zhenfeng Wang, Wenkai Zhong, Yuan Li*, Fei Huang*, and Yong Cao Institute of Polymer Optoelectronic Materials & Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou , P. R. China msfhuang@scut.edu.cn, celiy@scut.edu.cn 1. Materials and Methods 1.1 Instrument. 1 H and 13 C NMR spectra were obtained on a Bruker Advance III 500 (500 MHz) nuclear magnetic resonance (NMR) spectroscope in deuterated solvents at room temperature with tetramethylsilane (TMS, (CH3)4Si) as the internal reference. MALDI- TOF MS spectra were measured on a Walters Maldi Q-TOF Premier mass spectrometry. (TGA) measurements were performed using a Netzsch TG 209 thermogravimetric analyzer under flowing nitrogen gas at a heating rate of 10 o C min 1. Differential scanning calorimetry (DSC) was recorded on a Netzsch DSC 204 analyzer under flowing nitrogen gas at a heating or cooling rate of 10 or 20 o C min 1. UV-vis absorption 1

2 spectra in solution (chloroform) and as thin film (on a quartz substrate) were recorded on a UV-3600 UV-VIS-NIR spectrophotometer. Photoluminescence spectra as thin film (on a quartz substrate) were recorded on a Horiba FluoroLog spectrophotometer. The electrochemical cyclic voltammetry (CV) experiments were conducted on a CHI600D electrochemical workstation under nitrogen atmosphere in a deoxygenated solution of 0.1 M tetrabutylammoniumhexafluorophosphate (Bu4NPF6) in acetonitrile solvent at the scan rate of 100 mv s 1, employing ferrocene as an internal reference, a glassy carbon electrode as working electrode, a saturated calomel electrode (SCE) as reference electrode and a platinum (Pt) wire as counter electrode. TEM topographic images were performed on a JEM 2100F Field Emission Electron Microscope. Atomic force microscopy (AFM) in the tapping mode for a 5 μm 5 μm image size were obtained by using a Bruker Multimode 8 Microscope. The Grazing Incidence Wide-Angle X-ray Scattering (GIWAXS) measurements were performed at the Xeuss 2.0 of Xenocs, using the MetalJet-D2 X-ray Source, 0.2 o incident angle and Pilatus3R 1M (Dectris) detector. And the GIWAXS samples were prepared on silicon substrates by spin coating from the identical blend solutions as those used in devices. 1.2 Materials. All reagents and solvents, unless stated otherwise, were purchased from Rrichjoint, Energy Chemical Ltd, Suna Tech, and Guangzhou chemical reagent factory, were used without further purification. 5,5'-(4,8-diethynylbenzo[1,2-b:4,5-b']dithiophene-2,6- diyl)bis(4-(2-ethylhexyl)thiophene-2-carbaldehyde) (compound 7) and 5-bromo-2,9-2

3 1.3 Synthesis of Monomers. Synthesis di(undecan-6-yl)anthra[2,1,9-def:6,5,10-d'e'f']diisoquinoline-1,3,8,10(2h,9h)- tetraone (compound 9) were synthesized according to the literature. 1,2,3 PBDB-T and PTB7-Th were purchased from Solarmer Materials Inc. RDN and IT-F were purchased from Alfa Aesar. 4,8-bis((triisopropylsilyl)ethynyl)benzo[1,2-b:4,5- b']dithiophene(compound 3). Compound 2 (6.31 g, 35.0 mmol) and dry THF (75 ml) were added into an oven-dried 250 ml double-necked round-bottomed flask, the reaction container was purged with argon for 20 minutes, and then 2.5 M n-butyllithium in hexane (15.2 ml, 38.0 mmol) was added dropwise slowly at -78 under argon atmosphere. The mixture was stirred at 78 for 2 hours, and then compound 1 (2.54 g, 12.0 mmol) was added, and then the mixture was slowly warmed up to room temperature. After stirring for 2.5 hours, anhydrous stannous chloride (17.50 g, 92.0 mmol) was added and the solution was stirred overnight at room temperature. Brine (75 3

4 Synthesis ml) was added and the mixture was extracted with dichloromethane (3 50 ml). The organic phase was dried over anhydrous MgSO4 and filtered. After removing the solvent from the filtrate, the residue was purified by column chromatography on silica gel using petroleum ether as eluent, yielding a light yellow solid (4.64 g, 73%). 1 H NMR (500 MHz, CDCl3, ppm): δ 7.61 (d, J = 5.5 Hz, 2H), 7.56 (d, J = 5.5 Hz, 2H), (m, 42H). 13 C NMR (125 MHz, CDCl3, ppm): δ , , , , , , , 77.25, 77.00, 76.75, 18.76, 18.43, 18.16, 11.81, MS (APCI- HRMS): calcd for C32H46S2Si2, ; found [M], ((2,6-bis(trimethylstannyl)benzo[1,2-b:4,5-b']dithiophene-4,8- diyl)bis(ethyne-2,1-diyl))bis(triisopropylsilane) (compound 4). Compound 3 (3.86 g, 7.0 mmol) was added into an oven-dried 250 ml double-necked round-bottomed flask, the reaction container was degassed several times with argon followed by the addition of N,N,N0,N0-tetramethylethylene-diamine (TMEDA) (3.25 g, 28.0 mmol) and dry THF (90 ml). To the mixture was added 2.5 M n-butyllithium in hexane (11.7 ml, 28.0 mmol) dropwise slowly at -78 under argon atmosphere, and then the mixture was stirred at 78 for 2 hours to afford a yellow slurry. To the slurry was added a solution of trimethylstannyl chloride (35.0 ml,1.0 M) dropwise at 78, and then the mixture was slowly warmed up to room temperature. After stirring for 12 hours, brine (50 ml) was added and the mixture was extracted with ether (3 50 ml). The organic phase was dried over anhydrous MgSO4 and filtered. After removing the solvent from the filtrate, the residue was recrystallized from isopropyl alcohol gave a light yellow solid (4.61 g, 75%). 1 H NMR (500 MHz, CDCl3, ppm): δ 7.69 (s, 2H), 1.25 (d, J = 2.5 Hz, 42H),

5 (s, 18H). 13 C NMR (125 MHz, CDCl3, ppm): δ (s), (s), (s), HRMS): calcd for C38H62S2Si2Sn2, ; found [M], Synthesis b']dithiophene-2,6-diyl)bis(4-(2-ethylhexyl)thiophene-2-carbaldehyde) (compound 6). Compound 4 (2.0 g, 2.28 mmol), compound 5 (2.42 g, 7.99 mmol), and dry toluene (50 ml) were added into an oven-dried 75 ml reaction tube. The reaction tube was purged with argon for 20 minutes, and then the catalyst (PPh3)4Pd (10%eq, mmol, mg) were added under argon atmosphere. After another flushing with argon for 20 min, the mixture was heated to reflux for 12 hours gave an orange solution. After cooling to room temperature, the mixture was extracted with dichloromethane (3 50 ml). The organic phase was dried over anhydrous MgSO4 and filtered. After removing the solvent from the filtrate, the residue was purified by column chromatography on silica gel using petroleum ether/dichloromethane (5:2, v/v) as an eluent, yielding an orange solid (1.73 g, 76%). 1 H NMR (500 MHz, CDCl3, ppm): δ 9.90 (d, J = 1.0 Hz, 2H), 7.75 (t, J = 2.9 Hz, 2H), 7.63 (s, 2H), 2.86 (dd, J = 12.4, 7.3 Hz, 4H), (m, 2H), (m, 58H), 0.87 (m, 12H). 13 C NMR (125 MHz, CDCl3, ppm): δ , , , , , , , , , , , 77.25, 77.00, 76.75, 40.25, 33.71, 32.48, 28.63, 25.80, 22.97, 18.77, 14.03, 11.28, MS (APCI-HRMS): calcd for C58H82O2S4Si2, ; found [M], Synthesis (s), (s), (s), (s), (m), (s), (s). MS (APCI- 5,5'-(4,8-bis((triisopropylsilyl)ethynyl)benzo[1,2-b:4,5-5,5'-(4,8-diethynylbenzo[1,2-b:4,5-b']dithiophene-2,6-diyl)bis(4-(2- ethylhexyl)thiophene-2-carbaldehyde) (compound 7). In an oven-dried 250 ml 5

6 double-necked round-bottomed flask, compound 6 (3.31 g, 3.32 mmol) was dissolved in anhydrous THF (110 ml) followed by the addition of potassium hydroxide solution (2.5 M, 13.0 ml)and methanol (1.5 ml) successively, and then the reaction mixture was heated to 60 for 4 hours. After cooling to room temperature, the reaction mixture was poured into water and extracted with dichloromethane (3 50 ml). The organic phase was dried over anhydrous MgSO4 and filtered. After removing the solvent from the filtrate (The rotary temperature is no more than 45 o C), the residue was purified by column chromatography on silica gel using petroleum ether/dichloromethane (2:1, v/v) as eluent, yielding an orange solid (2.07 g, 91%). 1 H NMR (500 MHz, CDCl3, ppm): δ 9.91 (d, J = 1.5 Hz, 2H), 7.76 (s, 2H), 7.62 (s, 2H), 3.92 (d, J = 0.9 Hz, 2H), 2.88 (d, J = 7.3 Hz, 4H), 1.73 (dd, J = 11.9, 5.8 Hz, 2H), (m, 16H), 0.90 (m, 12H). 13 C NMR (125 MHz, CDCl3, ppm): δ , , , , , , , , , 87.98, 78.86, 77.25, 77.00, 76.75, 40.19, 33.73, 32.55, 28.70, 25.67, 23.03, 14.08, MS (MALDI-TOF): calcd for C40H42O2S4, ; found [M +], Synthesis 5-bromo-2,9-di(undecan-6-yl)anthra[2,1,9-def:6,5,10- d'e'f']diisoquinoline-1,3,8,10(2h,9h)-tetraone (compound 9). Compound 8 (1.83 g, 2.62 mmol) and anhydrous potassium carbonate (1.45 g, mmol) were added into an oven-dried 150 ml double-necked round-bottomed flask, and then 60 ml of dichloromethane was added. Liquid bromine (0.22 ml, 0.13 mol) was added dropwise 6

7 through a dropping funnel over 20 minutes, and the mixture was stirred at 35 C for 3 days. After cooling to room temperature, the reaction mixture was poured into ice-water followed by the addition of sodium thiosulfate solution with vigorous stirring to remove the excess liquid bromine. The mixture was extracted with dichloromethane (3 50 ml) and the organic phase was dried over anhydrous MgSO4 and filtered. After removing the solvent from the filtrate, the residue was purified by column chromatography on silica gel using petroleum ether/dichloromethane (4:3, v/v) as eluent, yielding a red solid (1.08 g, 53%). 1 H NMR (500 MHz, CDCl3, ppm) δ: 9.78 (d, J = 8.3 Hz, 1H), 8.91 (s, 1H), 8.69 (s, 3H), 8.61 (d, J = 7.9 Hz, 2H), 5.18 (dd, J = 8.0, 4.7 Hz, 2H), 2.24 (s, 4H), (m, 4H), 1.28 (qdd, J = 10.5, 8.0, 5.4 Hz, 24H), 0.83 (t, J = 6.9 Hz, 12H). 13 C NMR (125 MHz, CDCl3, ppm) δ: , , , , , , , , , , , , , , , , 77.25, 77.00, 76.75, 54.93, 54.74, 32.24, 31.70, (s), 29.66, 26.57, , MS (APCI-HRMS): calcd for C46H53BrN2O4, ; found [M + H], Synthesis of PDIBDT-CHO(10). Compound 7 ( mg, 0.8 mmol), compound 9 (1.43 g, 1.84 mmol), 7

8 Bis(triphenylphosphine)palladium(II) chloride (15%eq, 0.12 mmol, mg) and Copper iodide (20%eq, 0.16 mmol, mg) were added into an oven-dried 25 ml double-necked round-bottomed flask, the reaction container was degassed several times with argon. To this mixture 11.0 ml of dry chlorobenzene and 1.1 ml of diisopropylamine (DIPA) were added by syringe successively. The resultant mixture was stirred at room temperature for 24 hours to afford a reddish black solution, and then water (9.0 ml) was added to quench the reaction. The resulting mixture was extracted with chloroform (3 ml 50 ml) and the combined organic extracts were washed with brine. The organic mixture was dried over anhydrous MgSO4. After filtration, the low boiling point solvent was removed by rotary evaporation to give a black liquid. The crude product was purified by column chromatography using petroleum ether/dichloromethane (2:3, v/v) as the eluent to afford PDIBDT-CHO (10) as a black solid (1.15 g, 69 %). 1 H NMR (500 MHz, CDCl3, ppm) δ: (d, J = 8.2 Hz, 2H), 9.95 (s, 2H), 9.04 (d, J = 11.0 Hz, 2H), (m, 10H), 8.03 (s, 2H), 7.67 (s, 2H), (m, 4H), 2.95 (d, J = 7.2 Hz, 4H), 2.27 (dd, J = 13.3, 10.1 Hz, 8H), (m, 8H), 1.72 (dt, J = 12.5, 6.3 Hz, 2H), (m, 64H), (m, 30H), 0.61 (t, J = 7.3 Hz, 6H). 13 C NMR (125 MHz, CDCl3, ppm) δ: , , , , , , , , , , , , , 77.25, 77.00, 76.75, 54.76, 40.27, 33.75, 32.35, 31.74, 28.56, 26.63, 25.57, 22.88, 22.55, 13.96, MS (MALDI-TOF). Calcd for C132H146N4O10S4, ; found [M + Na], Element Anal. Calcd for C132H146N4O10S4: C 76.34, H 7.09, N 2.70; found: C 76.50, H 7.16, N

9 Synthesis of PDIBDT-RDN(11). Compound 10 (120.0 mg, mmol), compound 3-ethylrhodanine (46.6 mg, mmol) and chloroform (35 ml) were added into an oven-dried 100 ml doublenecked round-bottomed flask. The reaction container was purged with argon for 20 minutes, then triethylamine (1.0 ml) was added and refluxed for 72 hours under argon atmosphere to afford an apricot pink solution. After cooling to room temperature, the mixture was directly purified by silica gel ( mesh) column chromatography by using petroleum ether/dichloromethane (2:3, v/v) as eluent, and then the resulting material was further purified by gel column chromatography (THF as eluent), silica gel ( mesh) column chromatography (dichloromethane as eluent) successively to afford PDIBDT- RDN (11) as a black solid (116.5 mg, 85 %). 1 H NMR (500 MHz, CDCl3, ppm) δ: (d, J = 8.2 Hz, 2H), 9.00 (s, 2H), 8.75 (m, 10H), 8.00 (s, 2H), 7.63 (s, 2H), 7.07 (s, 2H), 5.23 (s, 2H), 5.12 (s, 2H), 4.10 (s, 4H), 2.97 (s, 4H), 2.29 (s, 4H), 2.10 (s, 4H), 1.88 (m, 8H), 1.71 (d, J = 5.6 Hz, 2H), (m, 64 H), 0.85 (t, J = 6.9 Hz, 12H), 0.81 (d, J = 6.2 Hz, 24H), 0.60 (t, J = 7.2 Hz, 6H). MS (MALDI- TOF): calcd for C 142 H 156 N 6 O 10 S 8, ; found [M + Na], Element Anal. Calcd for C142H156N6O10S8: C 72.17, H 6.65, N 3.56; found: C 72.04, H 6.70, N Synthesis of PDIBDT- IT(12). 9

10 Compound 10 (167.0 mg,0.080 mmol), compound 2-(3-oxo-2,3-dihydro-1Hinden-1-ylidene)malononitrile (78.1 mg,0.402 mmol) and chloroform (35 ml) were added into an oven-dried 100 ml double-necked round-bottomed flask. The reaction container was purged with argon for 20 minutes, then pyridine (1.0 ml) was added and refluxed for 15 hours under argon atmosphere to afford a purple solution. After cooling to room temperature, the mixture was directly purified by silica gel ( mesh) column chromatography by using petroleum ether/dichloromethane (2:3, v/v) as eluent, and then the resulting material was further purified by gel column chromatography (THF as eluent), silica gel ( mesh) column chromatography (dichloromethane as eluent) successively to afford PDIBDT-IT (12) as a black solid (194.3 mg,83 %). 1 H NMR (500 MHz, CDCl3, ppm) δ: (s, 2H), 8.99 (s, 4H), 8.63 (m, 14H), 7.67 (s, 4H), 7.60 (s, 4H), δ 5.21 (s, 2H), 4.97 (s, 2H), 2.94 (s, 4H), 2.27 (s, 4H), 1.91 (s, 8H), 1.74 (s, 6H), (m, 64H), (m, 30H), 0.56 (m, 6H). MS (MALDI-TOF): calcd for C 156 H 154 N 8 O 10 S 4, ; found [M + Na], Element Anal. Calcd for C 156 H 154 N 8 O 10 S 4 : C 77.13, H 6.39, N 4.61; found: C 77.02, H 6.44, N Synthesis of PDIBDT-ITF(13). Compound 10 (125.0 mg, mmol), compound 2-(6-fluoro-3-oxo-2,3- dihydro-1h-inden-1-ylidene)malononitrile (63.9 mg,0.301 mmol ) and chloroform (35 ml) were added into an oven-dried 100 ml double-necked round-bottomed flask. The reaction container was purged with argon for 20 minutes, then pyridine (1.0 ml) was added and refluxed for 15 hours under argon atmosphere to afford a dark purple solution. 10

11 After cooling to room temperature, the mixture was directly purified by silica gel ( mesh) column chromatography by using petroleum ether/dichloromethane (2:3, v/v) as eluent, and then the resulting material was further purified by gel column chromatography (THF as eluent), silica gel ( mesh) column chromatography (dichloromethane as eluent) successively to afford PDIBDT-ITF (13) as a black solid (125.7 mg,85 %). 1 H NMR (500 MHz, CDCl3, ppm) δ: (s, 2H), 8.97 (s, 4H), 8.74 (s, 10H), 8.23 (s, 2H), 8.11 (s, 2H), 7.73 (s, 2H), 7.60 (s, 2H), 7.31 (m, 2H), 5.20 (s, 2H), 4.96 (s, 2H), 2.92 (s, 4H), 2.26 (s, 4H), 1.91 (s, 8H), 1.73 (s, 6H), (m, 64H), (m, 30H), 0.55 (m, 6H). MS (MALDI-TOF): calcd for C 156 H 152 F 2 N 8 O 10 S 4, ; found [M + Na], Element Anal. Calcd for C 156 H 152 F 2 N 8 O 10 S 4 : C 76.01, H 6.21, N 4.55; found: C 75.94, H 6.24, N Optimized geometric structures PDIBDT-RDN PDIBDT-IT PDIBDT-ITF Top View Side View Figure. S1 The optimized geometric structures by density functional theory calculations for PDIBDT-RDN, PDIBDT-IT and PDIBDT-ITF. 11

12 3. Thermal Properties Analyses Figure. S2 Thermogravimetry (TGA) and differential scanning calorimetry (DSC) curves of PDIBDT-RDN, PDIBDT-IT, and PDIBDT-ITF. 12

13 4. UV-vis Spectroscopy 13

14 Figure. S3 Normalized UV-vis absorption spectra of the PDIBDT-CHO, PDIBDT- RDN, PDIBDT-IT, and PDIBDT-ITF in chloroform solution (a), and as thin film (b), UV-Vis spectra of PTB7-Th:Acceptor blend films (c). 5. Device Fabrication and Characterization. The PSCs were fabricated with the structure of ITO/PEDOT: PSS /active layer/p FN-Br/Ag. Before fabrication of the device, the indium tin oxide (ITO)-coated glass substrates were cleaned by a surfactant scrub and washed by water, acetone and isopropanol, successively, and finally dried in oven at 80 o C for 12 h before used. Then, a thin layer of PEDOT: PSS was deposited through spin-coating on the precleaned ITOcoated glass from a PEDOT: PSS aqueous solution, and dried subsequently at 150 C for 15 min in air. Subsequently, the device was transferred to a nitrogen glove box, and the PTB7-Th: PDIBDT- RDN, PTB7-Th:PDIBDT-IT or PTB7-Th: PDIBDT-ITF blend 14

15 was fully dissolved in chlorobenzene (CB) at a weight concentration of 10 mg/ml, and 1,8-iodooctane (DIO) was used as solvent additive. After that, the PTB7-Th: PDIBDT- RDN, PTB7-Th:PDIBDT-IT or PTB7-Th: PDIBDT-ITF active layer was spin coated from the mixed solution at various spinrate. For the devices needed annealing, an extra pre-annealing at 80 o C or other temperature for 10 min was performed. Then, a thin PFN-Br layer (5 nm) was then spin coated onto the active layer as the cathode interface layer. Finally, the substrates were transferred to a vacuum thermal evaporator, and top Ag electrode was deposited in vacuum onto the PFN-Br cathode buffer layer at a pressure of Torr through a shadow mask. The current density-voltage (J-V) curves of PSCs were measured with computer-controlled Keithley 2400 source meter under 1 sun, AM 1.5 G spectra (100 mw cm -2 ) from a solar simulator. The EQE spectra measurements were performed on a commercial QE measurement system (QE- R3011, Enlitech). 6. Photovoltaic properties. Table S1. Photovoltaic parameters of the NF-PSCs based on the PBDB-T: PDIBDT- RDN (w/w=1:1) active layer with various spinrate Spinrate (rpm) V oc (V) J sc (ma cm -2 ) FF (%) PCE (%) (120 C, 10 min) Table S2. Photovoltaic parameters of the NF-PSCs based on the PBDB-T: PDIBDT-IT 15

16 (w/w=1:1) active layer with various spinrate Spinrate (rpm) V oc (V) J sc (ma cm -2 ) FF (%) PCE (%) (120 C, 10 min) Table S3. Photovoltaic parameters of the NF-PSCs based on the PBDB-T: PDIBDT-IT active layer with various D/A ratios at different spinrate D/A (wt/wt) 2:1 1:1 1:2 Spinrate (rpm) V oc (V) J sc (ma cm -2 ) FF (%) PCE (%) Table S4. Photovoltaic parameters of the NF-PSCs based on the PBDB-T: PDIBDT-IT (w/w=1:1) active layer under different annealing temperature for 10 minutes. Annealing temperature ( C) V oc (V) J sc (ma cm -2 ) FF (%) PCE (%) None Table S5. Photovoltaic parameters of the NF-PSCs based on the PBDB-T: PDIBDT-IT 16

17 (w/w=1:1) active layer with various amounts of additive. Additive None 0.25% DIO 0.5% DIO 1% DIO Spinrate (rpm) V oc (V) J sc (ma cm -2 ) FF (%) PCE (%) Hole and Electron Mobility Measurement by Space Charge Limited Current (SCLC) Figure. S4 hole-only of blend films of J 1/2 V characteristics. 17

18 Figure. S5 electron-only of blend films of J 1/2 V characteristics. Figure. S6 electron-only of neat films of J 1/2 V characteristics. 18

19 8. NMR Spectra Figure. S7 1 H NMR spectrum of compound 10. Figure. S8 13 C NMR spectrum of compound

20 Figure. S9 1 H NMR spectrum of compound 11. Figure. S10 1 H NMR spectrum of compound

21 Figure. S11 1 H NMR spectrum of compound MALDI-TOF Spectrum 21

22 Figure. S12 MALDI-TOF spectrum of compound 10. Figure. S13 MALDI-TOF spectrum of compound 11. Figure. S14 MALDI-TOF spectrum of compound 12 22

23 Figure. S15 MALDI-TOF spectrum of compound 13. References (1) Rajasingh, P.; Cohen, R.; Shirman, E.; Shimon, L. J. W.; Rybtchinski, B. Selective Bromination of Perylene Diimides under Mild Conditions. J. Org. Chem. 2007, 72, (2) Mishra, R.; Regar, R.; Singhal, R.; Panini, P.; Sharma, G. D.; Sankar, J. Porphyrin based push pull conjugates as donors for solution-processed bulk heterojunction solar cells: a case of metal-dependent power conversion efficiency. J. Mater. Chem. A. 2017, 5, (3) Xie, R. H.; Chen, Z. M.; Liu, Y.; Wang, Z. F.; Chen, Z. X.; Ying, L.; Huang, F.; Cao, Y. Cross-conjugated n-type polymer acceptors for efficient all-polymer solar cells. Chem. Commun. 2018, 54,