Supporting Information for

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1 Supporting Information for A New Thieno[3,2-b]thiophene-Based Acceptor: Tuning Acceptor Strength of Ladder-type N-type Materials to Simultaneously Achieve Enhanced Voc and Jsc of Nonfullerene Solar Cells Shao-Ling Chang, Fong-Yi Cao, Wen-Chia Huang, Po-Kai Huang, Kuo-Hsiu, Huang, Chain-Shu Hsu and Yen-Ju Cheng* Department of Applied Chemistry, National Chiao Tung University, 1001 University Road, Hsinchu, Taiwan yjcheng@mail.nctu.edu.tw CONTENT 1. General Measurement and Characterization S 2. Experimental Procedures S 3. TGA Analysis S 4. DSC Measurements S 5. Computational Details....6S 6. 1D-GIWAXS Intensity Profiles S 7. Fabrication and Characterization of OPV devices...11s 8. 1 H and 13 C NMR Spectra... 12S 9. References S 1S

2 1. General Measurement and Characterization. 1 H and 13 C NMR spectra were measured using Varian 400 MHz instrument spectrometer and obtained in deuterated chloroform (CDCl3) with TMS as internal reference unless otherwise stated, and chemical shifts (δ) are reported in parts per million. Absorption spectra were taken on a HP8453 UV-vis spectrophotometer. Differential scanning calorimetery (DSC) was conducted on a TA Q200 Instrument under nitrogen atmosphere at a heating/cooling rate of 10 C/min. Thermogravimetric analysis (TGA) was recorded on a Perkin-Elmer Pyris under nitrogen atmosphere at a heating rate of 10 C/min. Electrochemical cyclic voltammetry was conducted on a CH instruments electrochemical analyzer. A carbon glass was used as the working electrode and a Ag/AgCl electrode as the reference electrode, while 0.1 M tetrabutylammonium hexafluorophosphate in acetonitrile was the electrolyte. CV curves were calibrated using ferrocence as the standard, whose HOMO is set at -4.8 ev with respect to zero vacuum level. The HOMO energy levels were obtained from the equation HOMO = - (Eox onset -E (ferrocene) onset +4.8) ev. The LUMO levels were obtained from the equation LUMO = -(E red onset -E (ferrocene) onset +4.8) ev. 2S

3 2. Experimental Procedures Thieno[3,2-b]thiophene-2-carboxylic acid (1), BDCPDT-CHO, and FIC were synthesized as reported [S1-S3]. Scheme S1. Synthetic routes of BDCPDT-TTC and BDCPDT-FIC Synthesis of Compound 2. Thionyl chloride (2.6 g, 21.6 mmol) was slowly added dropwise to a solution of compound 1 (1.0 g, 5.4 mmol) in dry chloroform (11 ml) and dry DMF (0.1 ml), as catalyst. The mixture was stirred at 65 o C for one hour under N2 atmosphere. After removal of the solvent and the excess thionyl chloride under reduced pressure, the residue was recrystallized from methanol to give a white solid 2, which was used for next step without further purification. Synthesis of Compound 3. To a stirred solution of malonyl dichloride (3.4 g, 24.4 mmol) and AlCl3 (4.34 g, 32.6 mmol) in dry dichloromethane (13.5 ml), then compound 2 (1.1 g, 5.43 mmol) was slowly added. The mixture was stirred at 65 o C for 12 h under N2 atmosphere. After cooling to room temperature, the mixture was poured into a 10% w/v aqueous solution of oxalic acid slowly. Then, the ph of the solution was tuned close to 7 by using 3S

4 NaHCO3 aqueous solution. The residue was extracted by dichloromethane (50 ml 2). The combined organic layer was dried over MgSO4. After removal of the solvent under reduced pressure, the residue was purified by column chromatography on silica gel (CH2Cl2) to give a yellow solid 3 (588 mg, 52 %). 1 H NMR (CDCl3, 400 MHz): δ 7.83 (d, J = 5.2 Hz, 1H), 7.44 (d, J = 5.6 Hz, 1H), 3.50 (s, 2H). 13 C NMR (CDCl3, 100 MHz): δ , , , , , , , , 48.69; HRMS (EI, C9H4O2S2): calcd, ; found, Synthesis of Compound 4. Compound 3 (0.1 g, 0.48 mmol) and malononitrile (0.05 g, 0.76 mmol) were dissolved in dimethylsulfoxide (2.5 ml), then anhydrous sodium acetate (0.06 g, 0.73 mmol) was added. The reaction was stirred at room temperature for 1h. The mixture was poured into water, and acidified to ph 1 2 by addition of the hydrochloric acid. The precipitate was filtered and purified by column chromatography on silica gel (CH2Cl2) to give a yellow solid TTC (68 mg, 55%). 1 H NMR (CDCl3, 400 MHz): δ 7.90 (d, J = 5.2 Hz, 1H), 7.88 (d, J = 5.2 Hz, 1H), 7.47 (d, J = 5.2 Hz, 1H), 7.46 (d, J = 5.6 Hz, 1H), 3.95 (s, 2H), 3.94 (s, 2H). 13 C NMR (CDCl3, 100 MHz): δ , , , , , , , , 77.32, 77.00, 76.68, ; HRMS (EI, C12H4N2OS2): calcd, ; found, Synthesis of BDCPDT-TTC. TTC (175 mg, 0.68 mmol) was added into the mixture of BDCPDT-CHO (180 mg, 0.17 mmol) in chloroform (34 ml) with pyridine (0.42 ml), the reactant was deoxygenated with nitrogen for 20 min. The reaction mixture was sealed and heated at 120 o C for 1 days. After cooling to room temperature and removal of the solvent under reduced pressure, the residue was then washed with methanol and hexane. The crude product was purified by silica gel column (hexane/dichloromethane, v/v, 1/1) to give a deep blue solid BDCPDT-TTC (132 mg, 51%). 1 H NMR (CDCl3, 400 MHz): δ 8.66 (s, 1H), 8.60 (s, 1H), 7.99 (s, 2H), 7.81 (d, J = 5.6 Hz, 1H), 7.78 (d, 4S

5 J = 5.6 Hz, 1H), 7.64 (s, 2H), 7.42 (d, J = 5.6 Hz, 1H), 7.41 (d, J = 4.0 Hz, 1H), 7.78 (d, J = 5.2 Hz, 1H), 7.16 (d, J = 6.8 Hz, 8H), 7.10 (d, J = 8.0 Hz, 8H), (m, 8H), (m, 24H), (m, 12H). 13 C NMR (CDCl3, 100 MHz): δ , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , 69.30, 66.83, 62.71, 35.55, 35.21, 33.41, 31.67, 31.24, 29.69, 29.10, 22.65, 22.39, 14.08, 13.93, 1.01.; HRMS (FD, C94H78N4O2S8): calcd, ; found, Synthesis of BDCPDT-FIC. FIC (100 mg, 0.09 mmol) was added into the mixture of BDCPDT-CHO (107 mg, mmol) in chloroform (18 ml) with pyridine (0.15 ml), the reactant was deoxygenated with nitrogen for 20 min. The mixture was deoxygenated with nitrogen for 20 min and then refluxed for 10 h. After cooling to room temperature and removal of the solvent under reduced pressure, the residue was then washed with methanol and hexane. The crude product was purified by silica gel column (hexane/dichloromethane, v/v, 1/1) to give a deep blue solid BDCPDT-FIC (80 mg, 58%). 1 H NMR (CDCl3, 400 MHz): δ8.86 (s, 1H), 8.53 (dd, J = 9.9, 6.5 Hz, 1H), 8.03 (s, 1H), 7.72 (s, 1H), 7.67 (t, J = 7.5 Hz, 1H), 7.16 (d, J = 8.4 Hz, 4H), 7.11 (d, J = 8.4 Hz, 4H), (m, 4H), (m, 4H), (m, 13H), (m, 6H). 13 C NMR (CDCl3, 100 MHz): δ , , , , , , , , , , , , , , , , , , , , , , , , , , , , , 69.23, 62.76, 35.54, 31.92, 31.66, 31.50, 31.23, 29.69, 29.65, 29.35, 29.09, 22.69, 22.56, 14.11, ; HRMS (FD, C94H78F4N4O2S4): calcd, ; found, S

6 3. TGA Analysis Figure S1. Thermogravimetric analyses of BDCPDT-TTC and BDCPDT-FIC at 4. DSC Measurements ramping rate of 10 o C/min. Figure S2. Differential scanning calorimetry of BDCPDT-TTC and BDCPDT-FIC. 5. Computational details Quantum chemical calculations were performed with the Gaussian09 suite [S4] employing the CAM-B3LYP density functional in combination with the 6 311G(d,p) basis set. Considering an insignificant effect on electronic properties, all the side-chain substituents were replaced with methyl groups. Geometry optimizations were performed with tight SCF and convergence criteria and an ultrafine integration grid by applying the GEDIIS optimization algorithm. The minimum nature of each stationary point was confirmed by a frequency analysis. Cartesian coordinates (Å) and energies (Hartree) of the Gaussian Cam- B3LYP/6 311G(d,p) optimized structures 6S

7 BDCPDT-TTC C C C C C C H H S S C C C C C C C C C C S C C C C C H C H C H H C C C C H S BDCPDT-FIC C C C C C C H H S S C C C C C C C C C C S C C C C C H C H C H H C C C C H

8 C H C H H C H H H C H H H C C C C C H C H C H H C C C C H C H C H H C H H H C H C H H C H H H C H H H C C C C C H C H C H H C C C C H C H C H H C H H H S

9 C H H H C C C C C C H C C C H H C C O C C O C C C N C N C N C N C S H C S C C H H H C C C C C C C C C C H H C C C C C C C H H H H C C O C C O C C C N C S

10 C C S H H S C C C C S H H N C N C N H C S H F F F F Figure S3. Experimental and Simulated absorption spectra of BDCPDT-TTC and its molecular orbitals. Table S1. Calculated a HOMO/LUMO energy, excitation energy, oscillator strength, and configuration (with large CI coefficients) of the excited state. 10S

11 6. 1D-GIWAXS Intensity Profiles Figure S4. (a) 2D GIWAXS patterns of blend films and (b) corresponding intensity profiles in the out-of-plane and in-plane directions. 7. Fabrication and Characterization of OPV devices For the inverted architectures, a ZnO precursor solution was spin coated onto ITOcoated glass and followed by thermal annealing at 170 C in air for 15 min to crystallize the film (thickness = ca. 50 nm). The detailed processing parameters (polymer/cb concentration; spin coating speed) are as follows: PBDB-T /BDCPDT-TTC (12 mg ml 1 ; 6000 rpm). An MoO3 layer (thickness = ca. 7 nm) and silver top anode (thickness = ca. 150 nm) were then thermally evaporated through a shadow mask under high vacuum (< Torr) to complete the inverted devices. Each device was constituted of 4 pixels defined by an active area of 0.04 cm 2. Finally, the J V curves were measured in air under an AM 1.5 G spectrum from a solar simulator. 11S

12 8. 1 H and 13 C NMR Spectra Figure S5. 1 H NMR spectrum of compound 3 at 300 K in CDCl3. Figure S6. 13 C NMR spectrum of compound 3 at 300 K in CDCl3. 12S

13 Figure S7. 1 H NMR spectrum of TTC at 300 K in CDCl3. Figure S8. 13 C NMR spectrum of TTC at 300 K in CDCl3. 13S

14 Figure S9. 1 H NMR spectrum of BDCPDT-TTC at 300 K in CDCl3. Figure S C NMR spectrum of BDCPDT-TTC at 300 K in CDCl3. 14S

15 Figure S11. 1 H NMR spectrum of BDCPDT-FIC at 300 K in CDCl3. Figure S C NMR spectrum of BDCPDT-FIC at 300 K in CDCl3. 15S

16 9. References [S1] K. Kawabata, M. Takeguchi, H. Goto, Macromolecules 2013, 46, [S1] S.-L. Chang, F.-Y. Cao, W.-C. Huang, P.-K. Huang, C.-S. Hsu, Y.-J. Cheng, ACS Appl. Mater. Interfaces 2017, 9, [S3] S. Dai, F. Zhao, Q. Zhang, T.-K. Lau, T. Li, K. Liu, Q. Ling, C. Wang, X. Lu, W. You, X. Zhan, J. Am. Chem. Soc. 2017, 139, [S4] Gaussian 09, Revision D.01, Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; et al. Gaussian, Inc., Wallingford CT, S