Supporting Information for Towards High Performance n-type Thermoelectric Materials by Rational Modification of BDPPV Backbones Ke Shi, Fengjiao Zhang, Chong-An Di,*, Tian-Wei Yan, Ye Zou, Xu Zhou, Daoben Zhu, Jie-Yu Wang*, and Jian Pei*, Beijing National Laboratory for Molecular Sciences, Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, Center for Soft Matter Science and Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China Table of Contents 1. General procedures and experimental details 2. Figures S1-S10 and Table S1-S2 3. Synthetic procedures and characterization 4. 1 H and 13 C NMR spectra S1
1. General procedures and experimental details Chemical reagents and CYTOP were purchased and used as received. All air and water sensitive reactions were performed under nitrogen atmosphere. 1 H and 13 C NMR spectra were recorded on Bruker ARX-400 (400 MHz). All chemical shifts were reported in parts per million (ppm). 1 H NMR chemical shifts were referenced to TMS (0 ppm), and 13 C NMR chemical shifts were referenced to CDCl3 (77.00 ppm). Mass spectra were recorded on a Bruker BIFLEX III mass spectrometer. Gel permeation chromatography (GPC) was performed on Polymer Laboratories PL-GPC220 at 140 o C using 1,2,4-tricholorobenzene (TCB) as eluent. Absorption spectra were recorded on PerkinElmer Lambda 750 UV-vis spectrometer. Cyclic voltammetry (CV) was performed on BASI Epsilon workstation. Thin film measurements were carried out in acetonitrile containing 0.1 M n-bu4npf6 as a supporting electrolyte. Glassy carbon electrode was used as a working electrode and a platinum wire as a counter electrode, and all potentials were recorded versus Ag/AgCl (saturated) as a reference electrode. Ultraviolet photoemission spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS) were conducted on a Kratos AXIS Ultra-DLD Photoelectron Spectrometer under an ultrahigh vacuum of about 3 10-9 Torr with an unfiltered He I gas discharge lamp source (21.22 ev) and a monochromatic Al Kα source (1486.6 ev) as the excitation source, respectively. For UPS measurements, the samples were biased at -9 V to observe the low-energy secondary electron cutoff. The instrumental energy resolution for UPS and XPS were 0.1 ev and 0.5 ev, respectively. Before measurements, all the samples were spin-coated on 1 cm 1 cm native oxide silicon substrates (detailed process was same as for OFET devices) in a N2 glove box and transferred through a transport system without air exposure in to the spectrometer analysis chamber. The X-ray diffraction data were recorded at beamline BL14B1 of the Shanghai Synchrotron Radiation Facility (SSRF) at a wavelength of 1.2379 Å. BL14B1 is a beamline based on bending magnet and a Si (111) double crystal monochromator was employed to monochromatize the beam. The size of the focus spot is about 0.5 mm and the end station is equipped with a Huber 5021 diffractometer. NaI scintillation detector was used for data collection. Atomic force microscopy studies were performed with a MultiMode8 microscope at tapping mode under ambient conditions. A silicon nitride cantilever (Budget Sensors Tap300Al) was used with a resonant frequency around 300 khz. Solution doping. Both BDPPV derivatives and N-DMBI were dissolved in 1,2- dichlorobenzene (o-dcb) with a concentration of 3 mg/ml. Aliquots of N-DMBI and polymer solutions were mixed at room temperature. OFET Film Fabrication and Characterization. Top-gate/bottom-contact FET devices were fabricated using n ++ -Si/SiO2 (300 nm) substrates. The gold source and drain bottom electrodes were patterned by photolithography on the SiO2 surface. The substrates were subjected to cleaning using ultrasonication in acetone, cleaning agent, S2
deionized water (twice), and isopropanol. The cleaned substrates were dried under vacuum at 80 o C for 2 h and then transferred into a glovebox. Thin films were deposited on the treated substrates by spin-coating at 1500 rpm for 60 s and annealed at 120 C for 8 h. After thin film deposition, a CYTOP solution (CTL809M:CT-solv180 = 3:1) was spin-coated onto the semiconducting layer at 2000 rpm for 60 s, resulting in a dielectric layer of 500 nm thick. The CYTOP layer was then baked at 100 o C for 1 h. Gate electrodes comprising a layer of Al (50 nm) were then evaporated through a shadow mask onto the dielectric layer by thermal evaporation. The OTFT devices had a channel length (L) of 5 μm and a channel width (W) of 200 μm. The evaluations of the FETs were carried out in atmosphere (humidity 50-60%) on a probe stage using Keithley 4200 SCS as parameter analyzer. Thermoelectric properties measurements. All devices were fabricated using glass substrates. The gold electrodes were pre-patterned by photolithography on the surface with a channel length of 100 μm and a channel width of 500 μm for conductivity measurements and a channel length of 500 μm and a channel width of 2500 μm for Seebeck coefficient measurements. The substrates were subjected to cleaning using the same procedures as above. Thin films were deposited on the treated substrates by spincoating at 1500 rpm for 60 s and annealed at 120 C for 8 h. The Seebeck coefficient measurements were done in vacuum. The Seebeck coefficient is calculated by S=Vtherm/ T, where Vtherm is the thermal voltage obtained between the two ends of the device subject to a temperature gradient T. The Vtherm was measured with Keithley 4200 SCS, and the temperature difference was introduced by Peliter elements and monitored by using an infrared camera FLIR A300 (thermal sensitivity < 50 mk). The accuracy of the measurements was verified by two resistive thermometers next to the electrodes. 4-Point conductivity measurements were conducted in an N2 glovebox with Keithley 4200 SCS. S3
2. Figures S1-S8 and Table S1 Table S1. Summary of electrochemical properties of three polymers E HOMO E LUMO E F E gap (ev) E gap (ev) (ev) (ev) (ev) (CV) (optical) BDPPV -6.20-4.01-4.36 2.19 1.42 ClBDPPV -6.29-4.30-4.50 2.00 1.39 FBDPPV -6.27-4.17-4.49 2.10 1.46 Figure S1. Cyclic voltammograms of BDPPV, ClBDPPV and FBDPPV in dropcasted film prepared using their chloroform solutions (1 mg/ml) Figure S2. Thin film absorption spectra of BDPPV derivatives under pristine and doping conditions (5 wt % of N-DMBI). S4
BDPPV ClBDPPV FBDPPV BDPPV-doped ClBDPPV-doped FBDPPV-doped Intensity (a.u.) 20 15 10 5 0 Binding Energy (ev) Figure S3. UPS measurements of BDPPV derivatives in pristine condition and doping condition (5 wt% of N-DMBI). Figure S4. a) Temperature difference dependent thermal voltage of 5 wt% N-DMBI doped BDPPV derivatives. b) The measured Seebeck coefficient under different channel length for 5 wt% N-DMBI doped BDPPV derivatives. S5
Figure S5. Temperature dependence of (a) electrical conductivity and (b) Seebeck coefficient for 5 wt% N-DMBI doped BDPPV derivatives. Figure S6. AFM height images of BDPPV derivatives. Films were prepared by spincoating their DCB solutions (3 mg/ml) and annealed at 120 o C for 8 h. S6
Normalized Intensity 1 0.1 0.01 BDPPV ClBDPPV FBDPPV BDPPV-doped ClBDPPV-doped FBDPPV-doped 5 10 15 20 25 2theta (degree) Figure S7. Out of-plane GIWAXS plots of BDPPV derivatives in pristine condition and doping condition (5 wt% of N-DMBI), which were obtained from a point detector in beamline BL14B1 (SSRF). Films were prepared by spin-coating their DCB solutions (3 mg/ml) and annealed at 120 o C for 8 h. Figure S8. N (1s) XPS spectra of BDPPV derivatives in doping conditions (a) (3 wt % of N-DMBI) and (b) (12 wt % of N-DMBI). S7
Table S2. The ratio of peaks at 402 ev and 400 ev at different doping conditions of BDPPV derivatives Ratio of peaks at 402 ev and 400 ev 3 wt % of N-DMBI 5 wt % of N-DMBI 12 wt % of N-DMBI BDPPV 15:85 25:75 26:74 ClBDPPV 20:80 33:67 35:65 FBDPPV 23:77 33:67 36:64 Figure S9. Transfer characteristics of N-DMBI-doped BDPPV derivatives OFETs at varied doping concentrations. (red: undoped; blue: 0.5 wt % N-DMBI-doped; orange: 1 wt % N-DMBI-doped; purple: 2 wt % N-DMBI-doped; green: 5 wt % N-DMBIdoped). Figure S10. Output characteristics of N-DMBI-doped BDPPV at different doping concentrations. S8
3. Synthetic procedures and characterization BDPPV, FBDPPV and N-DMBI were synthesized according to the literature. [1,2] Compound 1, 3 and 5 are commercially available. Sulfuryl chloride (63.7 mmol, 5 ml) was slowly added to a suspension of 6-bromoisatin (6 g, 26.5 mmol) in glacial acetic acid (150 ml) at 80 o C. The mixture was stirred for 6 h at 100 o C and then cooled at room temperature. The resulting solid was collected and washed with deionized water and dried in vacuum to afford 2 as a dark red solid (4.83 g, 70%). 2 is insoluble in common solvent and directly used for the next step without further purification. To a solution of 3 (2.78 g, 4.03 mmol) in a mixure of THF (30 ml) and N,N - dimethylformamide (DMF) (30 ml), 2 (1 g, 3.84 mmol) and K2CO3 (795 mg, 5.76 mmol) were added. The mixture was stirred at 50 o C for 8 h and then the solvents were removed under reduced pressure. The residue was dissolved in CHCl3 (100 ml) and then washed with water and brine, and dried over with Na2SO4. After removal of the solvents under reduced pressure, the residue was purified by silica gel chromatography with eluent (PE:CH2Cl2 = 1:1) to give 4 as an orange solid (2.21 g, 70 %). 1 H NMR (400 MHz, CDCl3, ppm): δ 7.65 (s, 1H), 7.18 (s, 1H), 3.66-3.69 (t, J = 8.0 Hz, 2H), 1.62-1.68 (m, 2H), 1.22-1.32 (m, 71H), 0.87-0.89 (t, J = 4.0 Hz, 6H); 13 C NMR (100 MHz, CDCl3, ppm): δ 181.6, 157.5, 149.3, 133.1, 130.0, 126.3, 117.4, 115.5, 41.0, 37.1, 33.5, 31.9, 30.7, 30.1, 29.7, 29.6, 29.4, 26.6, 24.3, 22.7, 14.1. ESI-HRMS calcd. for [C48H83BrClNO2 + H] + : 820.5374; Found: 820.5368. S9
To a solution of 4 (432 mg, 0.526 mmol) in acetic acid (15 ml), 5 (50 mg, 0.263 mmol) and p-toluenesulfonic acid monohydrate (14 mg, 0.074 mmol) were add under nitrogen atmosphere. The mixture was stirred at 115 ºC under nitrogen for 17 h. The mixture was then cooled to room temperature and filtered. The solid was washed with acetic acid and then methanol. The residue was purified by silica gel chromatography with eluent (PE:CHCl3 = 1:1) to give ClBDOPV as a black solid (222 mg, 47%). 1 H NMR (400 MHz, CDCl3, ppm): δ 9.06 (s, 2H), 9.01 (s, 2H), 6.94 (s, 2H), 3.68-3.72 (t, J = 8.0 Hz, 4H), 1.65-1.70 (m, 4H), 1.23-1.36 (m, 142H), 0.86-0.89 (t, J = 6.0 Hz, 12H); 13 C NMR (100 MHz, CDCl3, ppm): δ 166.6, 166.2, 151.9, 144.7, 134.5, 130.9, 128.8, 127.9, 127.0, 126.6, 120.6, 112.9, 111.3, 40.96, 37.15, 33.57, 31.9, 30.9, 30.2, 29.7, 29.6, 29.4, 26.7, 24.4, 22.7, 14.1. ESI-HRMS calcd. for [C106H168Br2Cl2N2O6 + H] + : 1794.0719; Found: 1794.0666. To a microwave vessel, ClBDOPV (120 mg, 0.0668 mmol), (E)-1,2- bis(tributylstannyl)ethene (40.5 mg, 0.0668 mmol), Pd2(dba)3 (2.6 mg, 4 mol%.), P(otol)3 (3.4 mg, 16 mol%), and 4 ml of chlorobenzene were added under nitrogen atmosphere. The vessel was then sealed with a snap cap under nitrogen atmosphere, and subjected to the following reaction conditions in a microwave reactor (120 ºC, 5 min; 140 ºC, 5 min; 160 ºC, 5 min; 180 ºC, 30 min). After completion, diethylphenylazothioformamide (5 mg) was added and then the mixture was stirred for 1 h at 100 ºC to remove any residual catalyst before being precipitated into methanol (200 ml). The precipitate was filtered through a nylon filter and purified via Soxhlet extraction for 8 h with acetone, 12 h with hexane, and finally was collected with chloroform. The chloroform solution was then concentrated by evaporation and precipitated into methanol (200 ml) and filtered off to afford a dark solid (103 mg, yield 93%). Elemental Anal. Calcd: for (C108H170Cl2N2O6)n: C, 77.98; H, 10.30; N, 1.68; Found: C, 77.44; H, 10.30; N, 1.64. Reference 1. (a) Lei, T.; Xia, X.; Wang, J.-Y.; Liu, C.-J.; Pei, J. J. Am. Chem. Soc. 2014, 136, 2135; (b) Lei, T.; Dou, J.-H.; Cao, X.-Y.; Wang, J.-Y.; Pei, J. J. Am. Chem. Soc. 2013, 135, 12168. 2. Zhu, X.-Q.; Zhang, M.-T.; Yu, A.; Wang, C.-H.; Cheng, J.-P. J. Am. Chem. Soc. 2008, 130, 2501. S10
4. 1 H and 13 C NMR spectra S11
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