SUPPLEMENTARY INFORMATION. Solution-Processed Organic Solar Cells Based on Dialkylthiol- Substituted Benzodithiophene Unit with Efficiency near 10%

Transcription

1 SUPPLEMENTARY INFORMATION Solution-Processed Organic Solar Cells Based on Dialkylthiol- Substituted Benzodithiophene Unit with Efficiency near 10% Bin Kan, # Qian Zhang, # Miaomiao Li, Xiangjian Wan, Wang Ni, Guankui Long, Yunchuang Wang, Xuan Yang, Huanran Feng, Yongsheng Chen* Key Laboratory of Functional Polymer Materials and the Center for Nanoscale Science and Technology, Institute of Polymer Chemistry, College of Chemistry, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University, Tianjin , China. Corresponding author: yschen99@nankai.edu.cn (YC) S1

2 1. Materials and Measurements. All reactions and manipulations were carried out under argon atmosphere with the use of standard Schlenk techniques. All starting materials were purchased from commercial suppliers and used without further purification unless indicated otherwise. ETL-1 was purchased from Lumtec. The 1 H and 13 C NMR spectra were recorded on a Bruker AV400 or 600 Spectrometer. High resolution MALDI spectra were collected with a Fourier transform-ion cyclotron resonance mass spectrometer instrument (Varian 7.0TFTICR-MS). Matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) were performed on a Bruker Autoflex III LRF200-CID instrument. The thermogravimetric analysis (TGA) was carried out on a NETZSCH STA 409PC instrument under purified nitrogen gas flow with a 10 C min -1 heating rate. UV Vis spectra were obtained with a JASCO V-570 spectrophotometer. Cyclic voltammetry (CV) experiments were performed with a LK98B II Microcomputer-based Electrochemical Analyzer. All CV measurements were carried out at room temperature with a conventional three-electrode configuration employing a glassy carbon electrode as the working electrode, a saturated calomel electrode (SCE) as the reference electrode, and a Pt wire as the counter electrode. Dichloromethane was distilled from calcium hydride under dry nitrogen immediately prior to use. Tetrabutylammonium phosphorus hexafluoride (Bu 4 NPF 6, 0.1 M) in dichloromethane was used as the supporting electrolyte, and the scan rate was 100 mv s -1. Atomic force microscopy (AFM) was performed using Multimode 8 atomic force microscope in tapping mode. The transmission electron microscopy (TEM) investigation was performed on Philips Technical G 2 F20 at 200 kv. The specimen for TEM measurement was prepared by spin casting the blend solution on ITO/PEDOT:PSS substrate, then floating the film on a water surface, and transferring to TEM grids. The GI-WAXS (Grazing incidence Wide-Angle X-ray Scattering) Samples were prepared on PEDOT:PSS-coated Si substrates using the same preparation conditions as for devices. The data were obtained with an area CCD S2

3 detector of 3072 by 3072 pixels resolution (225 mm by 225 mm) at beamline BL14B1 of the Shanghai Synchrotron Radiation Facility (SSRF). The monochromated energy of the X-ray source was 10 kev. The X-ray wavelength was Å and the incidence angle was In order to investigate the dependence of J ph on the light intensity, the intensity of the light was modulated with a series of two neutral density filters wheels of six filters, allowing for up to 18 steps in intensity from 100 to 2.88 mw cm -2. SCLC mobility was measured using a diode configuration of ITO/PEDOT:PSS/donor:PC 71 BM/Au for hole and Al/active layer/al for electron by taking the dark current density in the range of 0-8 V and fitting the results to a space charge limited form, where SCLC is described by: 9ε 0ε rµ 0V J = 3 8L 2 exp 0.89β V L where J is the current density, L is the film thickness of the active layer, µ 0 is the hole or electron mobility, ε r is the relative dielectric constant of the transport medium, ε 0 is the permittivity of free space ( F m -1 ), V (= V appl - V bi ) is the internal voltage in the device, where V appl is the applied voltage to the device and V bi is the built-in voltage due to the relative work function difference of the two electrodes. 2. Solar cell fabrication and testing. The devices were fabricated with a structure of glass/ito/pedot:pss/donor:acceptor/etl-1/al. The ITO-coated glass substrates were cleaned by ultrasonic treatment in detergent, deionized water, acetone, and isopropyl alcohol under ultra-sonication for 15 minutes each and subsequently dried by a nitrogen blow. A thin layer of PEDOT:PSS (Clevios P VP AI 4083, filtered at 0.45 µm) was spin-coated at 3000 rpm onto ITO surface. After baked at 150 C for 20 minutes, the substrates were transferred into an argon-filled glove box. Subsequently, the active layer was spin-coated from blend chloroform solutions with weight ratio of DR3TSBDT and PC 71 BM at 1:0.8 (or other ratios) and then annealed at 100 C for 10 min. After cooling to the room temperature, the substrates were placed in a glass petri dish containing 1 ml chloroform for 1 minute for solvent vapor annealing S3

4 (SVA). Then the substrates were removed. And ETL-1 solution (0.5 mg/ml, dissolved in methanol) was spin-coated at 3000 rpm. Finally, 80 nm Al layer were deposited under high vacuum (< Pa). The effective areas of cells were 4 mm 2 defined by shadow masks. The current density-voltage (J-V) curves of photovoltaic devices were obtained by a Keithley 2400 source-measure unit. All masked and unmasked tests gave consistent results with relative errors within 5%. The photocurrent was measured under illumination simulated 100 mw cm -2 AM 1.5G irradiation using an Oriel solar simulator, calibrated with a standard Si solar cell. The average PCE was obtained using 50 devices under the same conditions. External quantum efficiencies were measured using Stanford Research Systems SR810 lock-in amplifier. The thickness of the active layers in the photovoltaic devices was measured on a Veeco Dektak 150 profilometer. 3. Synthesis. Scheme S1. Synthesis route of DR3TSBDT. DCHO3TSBDT: A solution of compound 1 [1] (2.00 g, 1.9 mmol) and compound 2 (4.40 g, 4.4 mmol) in dry toluene (100 ml) was degassed twice with argon following S4

5 the addition of Pd(PPh 3 ) 4 (0.12 g, 0.1 mmol). After stirring and refluxing for 24 h at 110 o C with the protection of argon, the reaction mixture was poured into water (100 ml) and extracted with CH 2 Cl 2 (100 ml x 2). The organic layer was washed with water for twice and dried over anhydrous Na 2 SO 4 for 3 h. After removal of solvent, the crude product was purified by silica gel using dichloromethane/petroleum (3:1) as eluant to afford compound DCHO3TSBDT (2.00 g, 73%) as a red solid. 1 H NMR (400 MHz, CDCl 3 ): δ 9.82 (s, 2H), 7.68 (s, 2H), 7.59 (s, 2H), 7.24 (d, J = 3.86 Hz, 2H), 7.17 (s, 2H), 7.13 (d, J = 3.86 Hz, 2H), 4.24 (d, J = 4.24 Hz, 4H), (m, 8H), (m, 8H), (m, 16H), (m, 40H), (m, 24H); 13 C NMR(100 MHz, CDCl 3 ): δ , , , , , , , , , , , , , , , , , 40.31, 39.96, 32.24, 31.95, 30.45, 29.75, 29.60, 29.53, 29.49, 29.36, 29.31, 28.87, 25.59, 23.05, 23.05, 22.73, 14.16, MS (MALDI-TOF) m/z: calcd for C 84 H 114 O 2 S 10 [M] +, ; found, DR3TSBDT: DCHO3TBDT (0.27g, 0.2 mmol) and 3-ethyl rhodanine (0.33 g, 2 mmol) was dissolved in a dry CHCl 3 (50 ml) solution under the protection of argon, and then three drops of piperidine was added to the mixture. After stirring and refluxing for 12 h, the mixture was extracted with CHCl 3 (50 ml x 2), the organic layer was washed with water and dried over anhydrous Na 2 SO 4 for 3 h. After removal of solvent, the crude product was purified by silica gel using chloroform as eluant to afford DR3TSBDT as a black solid (0.30 g, 85%). 1 H NMR (400MHz, CDCl 3 ): δ 7.67 (s, 2H), 7.51 (s, 2H), 7.14 (br, 4H), 7.06 (br, 4H), (m, 4H), 2.97 (br, 4H), (br, 8H), (m, 8H), (m, 58H), (m, 30H); 13 C NMR(100 MHz, CDCl 3 ): δ , , , , , , , , , , , , , , , , , , , , , , , 65.60, 32.22, 32.00, 31.96, 30.58, 30.37, 30.19, 29.88, 29.57, 29.40, 28.88, 25.58, 23.09, 22.77, 19.21, 14.26, 14.20, 12.34, MS (MALDI-TOF) m/z: calcd for C 94 H 124 N 2 O 2 S 14 [M] +, ; found, Anal. Calcd. For C 70 H 86 N 6 O 2 S 7 : C, 64.04; H, 7.09; N, Found: C, 64.12; H, 7.11; N, S5

6 4. Thermogravimetric. Figure S1. TGA plot of DR3TSBDT with a heating rate of 10 o C min -1 under N 2 atmosphere. 5. UV-Vis absorption spectra. Figure S2. (a) UV-Vis absorption spectra of DR3TSBDT and DR3TBDT solutions; Table S1. Optical data of compounds DR3TSBDT and DR3TBDT. Compounds λmax (nm) Solution ε(λmax) (M 1 cm 1 ) λmax (nm) Pristine film ε(λmax) (cm -1 ) λonset (nm) Eg opt (ev) DR3TSBDT , DR3TBDT a , a Data from ref Cyclic voltammogram. S6

7 Figure S3. Cyclic voltammogram of DR3TSBDT in dichloromethane with 0.1 M Bu 4 NPF 6 as the supporting electrolyte at a scan speed of 100 mv s -1. The energy levels of the HOMO and LUMO were calculated from the onset oxidation potential and the onset reduction potential. Table S2. The electrochemical data of DR3TSBDT and DR3TBDT. molecules methods HOMO (ev) LUMO (ev) Eg (ev) DR3TSBDT Calculation CV -5.07(±0.02) -3.30(±0.03) 1.77 DR3TBDT a Calculation CV a Data from ref The chemical structure of ETL-1. Figure S4. The chemical structure of ETL Morphology analysis. S7

8 Figure S5. AFM topography images of DR3TSBDT:PC 71 BM blend films cast from chloroform solution: (a) as cast, the RMS roughness is 0.62 nm. (b) with TA treatment, the RMS roughness is 0.90 nm. (c) with TA&SVA treatment, the RMS roughness is 0.91 nm. Figure S6. The GIWAXS diffraction profiles for DR3TSBDT pure and blend films. 9. Mobility measurement. S8

9 Figure S7. Experimental dark-current densities for DR3TSBDT:PC 71 BM (w:w = 1:0.8) devices hole-only (a, b, c) and electron-only (d, e, f) devices. (a) (c) without post treatment. (b) (e) with TA. (c) (f) with TA&SVA. The solid lines represent the fit using a model of single carrier SCLC with field-independent mobility. The J D -V characteristics are corrected for the built-in voltage V bi that arises from the work function difference between the contacts. (a) cm 2 V -1 s -1 (b) cm 2 V -1 s -1 (c) cm 2 V -1 s -1 (d) cm 2 V -1 s -1 (e) cm 2 V -1 s -1 (f) cm 2 V -1 s J ph versus light intensity (P). Figure S8. Measured J ph plotted against light intensity in a double logarithmic scale both at low effective voltage (0.3 V) and high effective voltage (1.9 V). The fitted power law yields α are 1.00 and 0.95, respectively, which indicate little S9

10 bimolecular recombination in the optimal DR3TSBDT based device. 11. Photovoltaic performance. Figure S9. The J-V curve of a device based on DR3TSBDT:PC 71 BM (w:w=1:0.8) certified by National Center of Supervision & Inspection on Solar Photovoltaic Products Quality of China (CPVT). S10

11 Table S3. The average device performance parameters for BHJ solar cells based on DR3TSBDT. Treatment V oc (V) J sc (ma cm -2 ) FF PCE (%) None 0.96± ± ± ±0.24 TA 0.96± ± ± ±0.38 TA&SVA 0.91± ± ± ±0.35 Figure S10. J-V curves of BHJ solar cells based on DR3TSBDT:PC 71 BM with weight ratios (w:w) of 1:0.5 (square) 1:0.8 (triangle) and 1:1 (circle) cast from CHCl 3 with thermal annealing (TA) at 100 o C for 10 min using ETL-1/Al as the cathode under illumination of AM 1.5 G, 100 mw cm -2. Table S4. Photovoltaic performance of BHJ solar cells based on DR3TSBDT:PC 71 BM with weight ratios (w:w) of 1:0.5, 1:0.8 and 1:1 cast from CHCl 3 with TA at 100 o C for 10 min using ETL-1/Al as the cathode under illumination of AM 1.5 G, 100 mw cm -2. S11

12 Ratio of donor V oc (V) J sc (ma cm -2 ) FF PCE (%) and acceptor 1: : : Figure S11. J-V curves of BHJ solar cells based on DR3TSBDT:PC 71 BM with weight ratio at 1:0.8 with thickness of 90 nm (square), 110 nm (up-triangle), 130 nm (down-triangle) cast from CHCl 3 with TA at 100 o C for 10 min using ETL-1/Al as the cathode under illumination of AM 1.5 G, 100 mw cm -2. Table S5. Photovoltaic performance of BHJ solar cells based on DR3TSBDT:PC 71 BM with weight ratio at 1:0.8 with thickness of 90 nm (square), 110 nm (up-triangle), 130 nm (down-triangle) cast from CHCl 3 with TA at 100 o C for 10 min using ETL-1/Al as the cathode under illumination of AM 1.5 G, 100 mw cm -2. Thickness (nm) V oc (V) J sc (ma cm -2 ) FF PCE (%) S12

13 Figure S12. J-V curves of BHJ solar cells based on DR3TSBDT:PC 71 BM with weight ratio at 1:0.8 with different TA temperature using ETL-1/Al as the cathode under under illumination of AM 1.5 G, 100 mw cm -2. Table S6. Photovoltaic performance of BHJ solar cells based on DR3TSBDT:PC 71 BM with weight ratio at 1:0.8 cast from CHCl 3 with different TA temperature using ETL-1/Al as the cathode under illumination of AM 1.5 G, 100 mw cm -2. Temperature ( o C) V oc (V) J sc (ma cm -2 ) FF PCE (%) No S13

14 Figure S13. J-V curves of BHJ solar cells based on DR3TSBDT:PC 71 BM with weight ratio at 1:0.8 with thickness of 110 nm cast from CHCl 3 with TA at 100 o C for 10 min, and different time for SVA using ETL-1/Al as the cathode under illumination of AM 1.5 G, 100 mw cm -2. Table S7. Photovoltaic performance of BHJ solar cells based on DR3TSBDT:PC 71 BM with weight ratio at 1:0.8 with thickness of 110 nm cast from CHCl 3 with TA at 100 o C for 10 min, and different time for SVA using ETL-1/Al as the cathode under illumination of AM 1.5 G, 100 mw cm -2. SVA time (s) V oc (V) J sc (ma cm -2 ) FF PCE (%) NMR and MS spectra of DR3TSBDT. S14

15 Figure S14. 1 H NMR spectra of DR3TSBDT at 300K in CDCl 3. Figure S C NMR spectra of DR3TSBDT at 300K in CDCl 3. S15

16 Figure S16. MS (MALDI-TOF) spectrum of DR3TSBDT. Reference 1. Lee, D.; Stone, S. W.; Ferraris, J. P. Chem. Comm. 2011, 47, Zhou, J.; Wan, X.; Liu, Y.; Zuo, Y.; Li, Z.; He, G.; Long, G.; Ni, W.; Li, C.; Su, X.; Chen, Y. J. Am. Chem. Soc. 2012, 134, S16