Non-Fullerene Polymer Solar Cells Based on A Main-Chain Twisted Low Bandgap. Acceptor with Power Conversion Efficiency of 13.2%

Transcription

1 Supporting information Non-Fullerene Polymer Solar Cells Based on A Main-Chain Twisted Low Bandgap Acceptor with Power Conversion Efficiency of 13.2% Weiping Wang, a, Baofeng Zhao, a, Zhiyuan Cong, a, Yuan Xie, b Haimei Wu, a Quanbin Liang, b Sha Liu, b Feng Liu, c,* Chao Gao, a,* Hongbin Wu, b,* Yong Cao b a State Key Laboratory of Fluorine & Nitrogen Chemicals, Xi an Modern Chemistry Research Institute, Xi an, Shaanxi, , P. R. China. chaogao1974@hotmail.com (C. Gao). b Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, , P. R. China. hbwu@scut.edu.cn (H. B. Wu) c Department of Physics and Astronomy, and Collaborative Innovation Center of IFSA (CICIFSA), Shanghai Jiaotong University, Shanghai, , P.R. China. fengliu82@sjtu.edu.cn (F. Liu). W. Wang, B. Zhao and Z. Cong contribute equally to this work. 1

2 Experimental Methods J52 was synthesized in our laboratory according to the literature. [1] Using gel permeation chromatography (GPC) method on a PLGPC220 instrument at 150 o C with 1,2,4-trichlorobenzene as eluent and polystyrene as standard, the weight-average molecular weight (M w ) of J52 is measured as 170 kda with a polydispersity index (PDI) of 3.2. All the other chemicals were purchased as reagent grade from Aladdin, J & K, and Alfa Aesar Chemical Co., and used without further purification, unless otherwise noted. Compound 1 was synthesized according to the modified routine of literatures. [2] Synthesis of 5-bromo-4-((2-ethylhexyl)oxy)thiophene-3-carbaldehyde (compound 2) The solution of 2-bromo-3-((2-ethylhexyl)oxy)thiophene (1.75 g, 6 mmol) in 10 ml anhydrous THF was added dropwise into LDA (20 ml, 7.5 mmol) at -35 o C. The mixture was stirred for 30 min at -35 o C. Then the anhydrous dimethyl formamide (DMF) (1.1 g, 15 mmol) was added in one portion, after that the low temperature bath was removed and the reaction was stirred to ambient temperature for another 1 h. The mixture was quenched by water and extracted by hexane. The organic phase was dried over anhydrous magnesium sulfate (MgSO 4 ) and then concentrated, further purification was carried out by silica gel column chromatography using hexane as eluent to obtain the pure compound 2 as a slightly yellow oil (1.2 g, yield 62.8%). 1 H NMR (CDCl 3, 500 MHz), δ (ppm): 9.84 (s, 1H), 6.87 (s, 1H), 4.00 (d, 2H), 1.73 (m, 1H), (m, 8H), (m, 6H). The isomer 5-bromo-4-((2-ethylhexyl)oxy)thiophene-2-carbaldehyde was also existed in the reaction system, which is a more yellow oily material with bigger polarity relative to compound 2. Synthesis of 5,5 -(4,4,9,9-tetrakis(4-hexylphenyl)-4,9-dihydro-s-indaceno[1,2-b:5,6-b']dithiophene-2,7- diyl)bis(4-((2-ethylhexyl)oxy)thiophene-3-carbaldehyde) (compound 3) Compound 1 (2.96 g, 2.4mmol) and 5-bromo-4-(2-ethylhexyloxy)- thiophene-3-carbaldehyde (compound 2) (2.80 g, 8.6 mmol) were dissolved in a 250 ml dry flask in degassed toluene (160 ml), the mixture was flushed with nitrogen for 30 min, then (Pd(PPh 3 ) 4 ) (240 mg) was added under nitrogen. After stirring the mixture at 90 o C overnight, the reaction was quenched with 100 ml water and extracted with ethyl acetate. Then, the combined organic solvent was washed with brine and dried over anhydrous magnesium sulfate. After removing the solvent, the compound 3 was purified with column chromatography on silica-gel using mixture of ethyl acetate (EA) and hexane (1: 100 by volume) as a red solid (2.90 g, 87.1%). 1 H NMR (500 MHz, CDCl 3 ), δ(ppm): 9.93 (s, 2H), 7.42 (s, 2H), 7.25 (s, 2H), 7.16 (d, 8H), 7.09 (d, 8H), 6.86 (s, 2H ), 4.05 (d, 4H), 2.57 (t, 8H), 1.76 (m, 2H), (m, 16H), (m, 32H), (m, 24H). 13 C 2

3 NMR (125 MHz, CDCl 3 ), δ(ppm): , , , , , , , , , , , , , , , , 74.53, 63.15, 39.52, 35.58, 31.73, 31.35, 30.41, 29.15, 29.03, 23.82, 22.99, 22.60, 14.10, 14.06, Anal.Calcd for (C 90 H 110 O 4 S 4 ): C 78.10, H 8.01, Found: C 78.52, H HRMS (MALDA) m/z: Anal.Calcd for [M+Na] , , ; Found: , , Synthesis of i-ieico-4f To a mixture of compound 3 (530 mg, 0.37 mmol) and 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1- ylidene)malononitrile (431 mg, 1.87 mmol) were dissolved in a dry flask in 50 ml chloroform, pyridine (1.2 ml) was added at room temperature. Then the mixture was vigorously stirred at 65 o C for 8 h. After cooling down, the mixture was extracted with chloroform. Then, the organic layer was dried over anhydrous magnesium sulfate and concentrated to afford the crude product. The crude product solution was poured into methanol and filtered through a Buchner funnel. Then the solid product of compound i-ieico-4f was purified by silica gel by using chloroform as eluent to give a black solid. (450 mg, 67.2%). 1 H NMR (500 MHz, CDCl 3 ), δ 9.13 (s, 2H),8.51 (dd, 2H), 7.61(t, 2H), 7.53 (s, 2H), 7.49 (s, 2H), 7.17(d, 8H), 7.12 (d, 8H), 6.91 (s, 2H ), 4.16 (m, 4H), 2.60 (t, 8H), 1.90 (m, 2H), (m, 16H), (m, 32H), (m, 24H). 13 C NMR (125 MHz, CDCl 3 ), δ , , , , , , , , , , , , , , , , , , , , , , 75.86, 67.35, 63.21, 39.30, 35.59, 31.75, 31.35, 30.02, 29.12, 28.95, 23.45, 23.01, 22.60, 14.10, Anal. Calcd for (C 114 H 114 F 4 N 4 O 4 S 4 ): C 75.71, H Found: C 75.60, H Measurement All the compounds were characterized by nuclear magnetic resonance spectra (NMR) in chloroform-d (CDCl 3 ) using tetramethylsilane (TMS) as the internal reference recorded on a Bruker AV 500 spectrometer at room temperature. The absorption spectra of the materials were measured by a PerkinElmer Lambda 750 UV/Vis/NIR spectrometer. Thermal stabilities of the acceptors were investigated on a Universal V2.6D TA instruments. The electrochemical cyclic voltammetry of the materials was conducted on a CHI 660D Electrochemical Workstation in a 0.1mol/L tetrabutylammonium hexafluorophosphate (Bu 4 NPF 6 ) acetonitrile solution, using glassy carbon, platinum wire, and Ag/Ag + electrode as working electrode, counter electrode, and reference electrode, respectively. Atomic force microscopy (AFM) images were collected under ambient conditions in air on a MultiMode scanning probe microscope (AFM, Veeco Multi Mode V). 3

4 Fabrication and characterization of the photovoltaic cells The device structure was ITO/ZnO/J52:acceptors/MoO 3 /Al. The carefully cleaned ITO glass was treated with ultraviolet-ozone for 20 min. Zinc acetate dihydrate dissolved in 2-methoxyethanol and a small amount of ethanolamine was spin-cast on ITO glass, and then baked at 200 o C for 60 min in air to form a 40 nm ZnO layer. The photoactive layer (80-90 nm) was prepared by spin-coating from the chlorobenzene (CB) solution of the NF acceptor and J52 (total concentration of 24 mg/ml) on the top of ITO/ZnO substrate in a glove box. Then a 10 nm MoO 3 layer and 120 nm Al layer were deposited subsequently in a vacuum evaporator. As determined by the shadow mask used during deposition of Al cathode, the effective area of the device was 0.16 cm 2. The PCE values of the unencapsulated devices were determined under atmospheric condition on a Keithley 2400 source meter from current density (J)-voltage (V) curve measurements under 1 sun, AM 1.5G spectrum from a monocrystal silicon cell (VLSI Standards Inc.) calibrated solar simulator (Newport model 94021A, 100 mw cm -2 ). After the J-V measurement, EQE of the corresponding PSCs were recorded under atmospheric condition on a QTEST 1000 AD Hyper mono light System (Crowntech Inc.). Carrier mobility measurement. To measure the hole and electron mobilities, space-charge limited current (SCLC) method was used in a devices structure of ITO/PEDOT:PSS (40nm)/Active layer/moo 3 (10 nm)/ag(100 nm) and ITO/ZnO(40nm) /Active layer/ca (10 nm)/al (100 nm) with the effective area of 0.16 cm 2, respectively, by taking the dark current density and fitting the results to a space charge limited form. [3] SCLC is described by the equation: J= 9ε 0 ε r μ 0 V 2 /8L 3, where J is the current density, ε 0 is the permittivity of free space ( F m -1 ), ε r is the relative dielectric constant of the transport medium, μ 0 is the hole or electron mobility, 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, L is the film thickness of the active layer. Morphology Characterization Grazing incidence x-ray diffraction (GIXD) characterization of active layer was performed at beamline 7.3.3, Advanced Light Source (ALS), Lawrence Berkeley National Lab (LBNL). X-ray energy was 10 kev and operated in top off mode. The scattering intensity was recorded on a 2D image plate (Pilatus 2M) with a pixel size of 172 m ( pixels). The samples were ~10 mm long in the direction of the beam path, and the detector was located at a distance of 300 mm from the sample center (distance calibrated by 4

5 AgB reference). The incidence angle was chosen to be 0.16 o (above critical angle) for GIXD measurement. OPV samples were prepared on PEDOT:PSS covered Si wafers in a similar manner to the OPV devices. RSoXS was performed at beamline Lawrence Berkeley National Lab. Thin films was flowed and transferred onto Si 3 N 4 substrate and experiment was done in transition mode. HOMO-1: ev HOMO: ev LUMO: ev LUMO+1: ev Figure S1. Calculated HOMO-1, HOMO, LUMO and LUMO+1 distribution for IEICO-4F. HOMO-1: ev HOMO: ev LUMO: ev LUMO+1: ev Figure S2. Calculated HOMO-1, HOMO, LUMO and LUMO+1 distribution for i-ieico-4f. Figure S3. 1 H NMR spectrum of compound 3. 5

6 Figure S4. 13 C NMR spectrum of compound 3. Figure S5. 1 H NMR spectrum of i-ieico-4f. 6

7 Weight Residue (%) Current/mA Figure S6. 13 C NMR spectrum of i-ieico-4f J52 E red onset = -1.81V E LUMO = ev E HOMO = ev E ox onset = 0.50V Voltage/V vs.ag/ag + Figure S7. Cyclic voltammogram of J52 film in diluted CH 3 CN solution with a scan rate of 100 mv s i-ieico-4f Temperature ( o C) Figure S8. Thermal gravimetric analysis (TGA) curve of i-ieico-4f. 7

8 Current density (ma/cm 2 ) Normalized Absorbance J52 J52: IEICO-4F J52: i-ieico-4f Wavelength (nm) Figure S9. Absorption spectra of J52, J52:IEICO-4F (1:1.3) and J52:i-IEICO-4F (1:1) films IEICO-4F as cast IEICO-4F 130 o C TA 10min i-ieico-4f as cast i-ieico-4f 130 o C TA 10min Voltage (V) Figure S10. J-V curves of as cast and 130 o C TA treated PSCs measured under illumination of AM 1.5 G condition, 100 mw cm -2 Table S1. Photovoltaic performances of as cast and TA treated PSCs measured under illumination of AM D/A J52:IEICO-4F=1:1.3 J52:i-IEICO-4F=1:1 1.5 G condition, 100 mw cm -2 Post treatment V OC [V] J SC [ma/cm 2 ] FF [%] PCE [%] As cast o C 10 min As cast o C 10 min

9 J 1/2 (A 1/2 m -1 ) J 1/2 (A 1/2 m -1 ) IEICO-4F As cast IEICO-4F-130 o C TA i-ieico-4f-as cast i-ieico-4f-130 o C TA V app -V bi -V a (V) a b V app -V bi -V a (V) IEICO-4F As cast IEICO-4F 130 o C TA i-ieico-4f As cast i-ieico-4f 130 o C TA Figure S11. J 1/2 vs V plots: J52:IEICO-4F and J52:i-IEICO-4F hole-only diode (a) and electron-only diode (b). Table S2. Measurement of the hole and electron mobilities. Active layer Post treatment Thickness Hole mobility Electron mobility (nm) (cm 2 V -1 s -1 ) (cm 2 V -1 s -1 ) J52:IEICO-4F As cast o C TA 10min J52:i-IEICO-4F As cast o C 10min Figure S12. Surface morphology of the blend films.(a) AFM height image of J52:IEICO-4F (1:1.3) as cast film (RMS=0.922 nm; (b) AFM height image of J52:IEICO-4F (1:1.3) 130 o C TA film (RMS=1.211 nm); (c) AFM height image of J52:i-IEICO-4F (1:1) as cast film (RMS=0.908 nm); (d) AFM height image of J52:i-IEICO-4F (1:1) 130 o C TA film (RMS=1.082 nm).surface morphology of the blend films: (a ) AFM phase image of J52:IEICO-4F as cast film; (b ) AFM phase image of J52:IEICO-4F 130 o C TA film; (c ) AFM phase image of J52:i-IEICO-4F as cast film; (d ) AFM phase image of J52:i-IEICO-4F 130 o C TA film. 9

10 Figure S13. TEM image of J52:IEICO-4F upon 130 o C TA treatment (a) and J52:i-IEICO-4F upon 130 o C TA treatment (b). REFERENCES: [1] H. Bin, Z.-G. Zhang, L. Gao, S. Chen, L. Zhong, L. Xue, C. Yang, Y. Li, J. Am. Chem. Soc., 2016, 138, [2] Y. Lin, J. Wang, Z.-G. Zhang, H. Bai, Y. Li, D. Zhu, X. Zhan, Adv. Mater., 2015, 27, [3] M. Zhang, J. Wang, F. Zhang, Y. Mi, Q. An, W. Wang, X. Ma, J. Zhang, X. Liu, Nano Energy, 2017, 39,