Supporting Information, by Li, et al

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1 Annealing-Free High Mobility Diketopyrrolopyrrole-Quaterthiophene Copolymer for Solution-Processed Organic Thin Film Transistors Yuning Li, 1,2,* Prashant Sonar, 1 Samarendra P. Singh, 1 Mui Siang Soh, 1 Martin van Meurs, 3 and Jozel Tan 3 1 Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology, and Research (A*STAR), 3 Research Link, Singapore ; 2 Department of Chemical Engineering and Waterloo Institute for nanotechnology (WIN), University of Waterloo, 200 University Avenue West, Waterloo, Ontario, Canada N2L 3G1; 3 Institute of Chemical and Engineering Sciences, A*STAR, 1 Pesek Road, Jurong Island, Singapore Experimental Section Instrumentation and materials. NMR data were collected on a Bruker DPX 400 MHz spectrometer with chemical shifts relative to tetramethylsilane (TMS, 0 ppm). UV-Vis-NIR spectra were recorded on a Shimadzu model 2501-PC instrument. Matrix assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectra were obtained on a Bruker Autoflex TOF/TOF instrument using dithranol as matrix. Differential scanning calorimetry (DSC) was measured under nitrogen on a TA Instrument DSC Q100 instrument at a scan rate of 10 C/min. Thermal gravimetric analysis (TGA) was carried out using a TA Instrument TGA Q500 at a heating rate of 10 C/min under nitrogen. Cyclic voltammetry (CV) measurements were performed on an Echochimie Autolab potentiostat (model PGSTAT30) using an Ag/AgCl reference electrode, a platinum wire counter electrode, and a platinum foil working electrode. The working electrode was coated with the polymer film by drop-casting a polymer solution in chloroform. CV measurements were recorded in 0.1 M tetrabutylammonium hexafluorophosphate in dry acetonitrile at a sweeping rate of 100 mv/s under nitrogen. The HOMO and LUMO energy levels S1

2 bis(2-octy1-dodecyl)-3,6-dithienyl-1,4-diketopyrrolo[3,4-c]pyrrole (2), 4 were calculated using the equations of E HOMO = E p ev and E LUMO = E n ev, respectively, where E p and E n are the onset potentials for oxidation and reduction, respectively, relative to the Ag/AgCl reference electrode. 1 X-ray diffraction patterns of thin films (~100 nm) on the OTS-modified Si/SiO 2 substrate deposited by drop-casting a polymer solution in chloroform was obtained with a PANalytical X PERT PRO system using Cu K α source. Two-dimensional X-ray diffraction (2-D XRD) measurements were performed on a stack of polymer thin films. The polymer thin films (~100 nm thick) were prepared by evaporating a dilute polymer solution in chloroform in a round-bottom flask, followed by rinsing with methanol to remove the thin films from the flask wall. 2 2-D XRD measurements were carried out on a Bruker AXS D8 system using Cu K α source in air. Data were analyzed with the GADDS software. Gel permeation chromatography (GPC) measurements were performed on a Waters 2690 System using THF as eluent and polystyrene as standards at a column temperature of 40 C. HT-GPC measurements were performed on a Polymer Labs GPC-220 equipped with a refractive index detector, a 500 µm injection loop, two PLgel Olexis columns (300 mm 7.5 mm, particle size: 13 µm) and one PLgel Olexis 13 µm guard column (50 mm 7.5 mm) at 160 C using 1,2,4-trichlorobenzene stabilized with g/l BHT as the eluent. Polymer solutions were prepared at a concentration of 0.3 mg/ml using a Polymer Labs SP260 sample preparation system at 160 C for 1 min, which resulted in complete dissolution of the polymers, followed by transfer to the GPC vials. The measured data were analyzed with Cirrus software, using narrow MWD polystyrene standards as a reference (PL EasiVial PS, range of calibration 10 3 to ). 2, 5-Dihydro-1, 4-dioxo-3, 6-dithienylpyrrolo [3, 4-c]-pyrrole (1), 3 N,N - 3,6-bis-(5-bromo-thiophen-2- yl)-n,n -bis((octyldodecyl)-1,4-dioxo-pyrrolo[3,4-c]pyrrole (3), 4 and 5,5 -bis(trimethylstannyl)- bithiophene 5 were synthesized according to the reported methods. Synthesis of PDQT. 3,6-Bis-(5-bromo-thiophen-2-yl)-N,N -bis((octyldodecyl)-1,4-dioxo-pyrrolo[3,4- c]pyrrole (0.306 g, 0.3 mmol), 5,5 -bis(trimethylstannyl)bithiophene (0.148 g, 0.3 mmol), S2

3 bis(triphenylphosphine)palladium(ii) dichloride (Pd(PPh 3 ) 2 Cl 2 ) (7 mg, 0.01 mmol), and anhydrous toluene (20 ml) were charged in a 50 ml flask under argon. The mixture was heated to 90 ºC and stirred for 48 hr. To the reaction mixture was then added 0.5 ml of bromobenzene to react with the residual trimethylstannyl end group. The mixture was further stirred at 90 ºC for 6 hr before cooling down to room temperature, and poured into 200 ml of stirring ethanol. The solid was filtered off, washed with methanol, and dried. Soxhlet extraction using acetone, methanol, and hexane was carried out to remove impurities and oligomers. The remaining product was dissolved with refluxing chloroform. A blue solid was obtained after removing the solvent (0.303 g, 98.7 %). Mp (DSC): C. 1 H NMR (400 MHz, CDCl 3 ): δ 0.85 (br), 1.22 (br), 3.05 (br), 4.01 (br), 6.85 (br), 8.95 (br). Anal. calcd for C 62 H 90 N 2 O 2 S 4 : C 72.75, H 8.86, N 2.74; found: C 71.33, H 8.89, N M w /M n (GPC) = 365,000/106,000 (40 C using THF as eluent); 60,600/25,400 (160 C using 1,2,4-trichlorobenzene as eluent). UV-vis-Near IR: 777 nm (in chloroform), 790 nm (thin film). Synthesis of PDQT-a. PDQT-a with a lower molecular weight was prepared under conditions similarly as above by terminating the polymerization after 24 hr. Data for PDQT-a follow. Yield: 99.7%. Mp (DSC) C. M w /M n (GPC) = 97,200/45,200 (column temperature: 40 C; eluent: THF); 50,700/21,100 (column temperature: 160 C; eleunt: 1,2,4- trichlorobenzene). UV-vis-Near IR: 772 nm (in chloroform); 792 nm (thin film). Fabrication and characterization of OTFT devices. A bottom-gate, top-contact TFT device configuration was used. The device was built on an n + -doped Si wafer with a layer of thermally grown SiO 2 (~200 nm) with a capacitance of ~17 nf/cm 2. The Si wafer functioned as the gate electrode while the OTS-modified SiO 2 layer acted as the gate dielectric. The substrate was cleaned and modified with octyltrichlorosilane prior to use. 4 A solution of PDQT (6 mg/ml) or PDQT-a (8 mg/ml) in chloroform was filtered through a 0.45 µm syringe filter and spin-coated on the substrate at 1200 rpm for 60 s at room temperature in a glove box. The polymer thin film (~35 nm) was optionally annealed on a S3

4 hotplate for 15 min under nitrogen. Subsequently, the gold source/drain electrode pairs (~100 nm in thickness) were deposited on top of the polymer thin film by high vacuum thermal evaporation through a shadow mask to define the channel length (L, 100 µm) and width (W, 1 mm). The measurements of the devices and calculation of the mobility and other device parameters were carried out similarly as reported previously. 4 Additional Figures: Figure S1. GPC elution curve and molecular weights of PDQT using THF as eluent at a column temperature of 40 C. S4

5 Figure S2. GPC elution curve and molecular weights of PDQT-a using THF as eluent at a column temperature of 40 C. Figure S3. GPC elution curve and molecular weights of PDQT using 1,3,4-trichlorobenzene as eluent at a column temperature of 160 C. S5

6 Figure S4. GPC elution curve and molecular weights of PDQT-a using 1,3,4-trichlorobenzene as eluent at a column temperature of 160 C Heat Flow (W/g) C W/g 34.07J/g C Exo Up Temperature ( C) Universal V3.0G TA Instruments (a) S6

7 2 1 Heat Flow (W/g) C W/g 28.71J/g C Exo Up Temperature ( C) Universal V3.0G TA Instruments Figure S5. DSC curves of PDQT (a) and PDQT-a (b) with heating rate 10 C/min under nitrogen. (b) Figure S6. TGA plot of PDQT at a heating rate of 10 C/min in nitrogen. S7

8 Figure S7. 2-D XRD data measured on a stack of PDQT-a thin films: 2-D transmission XRD images obtained with the incident X-ray parallel (a) and perpendicular (b) to the film stack; (c) and (d) are respective XRD diffractograms of pattern intensities of (a) and (b) obtained by integration of Chi (0-360 ) with GADDS software. References (1) (a) Leeuw, D. M.; Simenon, M. M. J.; Brown, A. R.; Einerhand, R. E. F. Synth. Met. 1997, 87, 53. (b) Cui, Y.; Zhang, X.; Jenekhe, S. A. Macromolecules 1999, 32, (c) Janietz, S.; Bradley, D. D. C.; Grell, M.; Giebeler, C.; Inbasekaran, M.; Woo, E. P. Appl. Phys. Lett. 1998, 73, (2) Pan, H.; Li, Y.; Wu, Y.; Liu, P.; Ong, B. S.; Zhu, S.; Xu, G. J. Am. Chem. Soc. 2007,129, (3) Li, Y. U. S. Patent Application 2009/65766 A1, (4) Li, Y.; Singh, S. P.; Sonar, P. Adv. Mater. 2010, 22, (5) Wei, Y.; Yang, Y.; Yeh, J.-M. Chem. Mater. 1996, 8, S8