Effects of Solubilizing Group Modification in Fullerene Bisadducts. on Normal and Inverted Type Polymer Solar Cells

Transcription

1 Effects of Solubilizing Group Modification in Fullerene Bisadducts on Normal and Inverted Type Polymer Solar Cells Supporting Information Ki-Hyun Kim,,a Hyunbum Kang,,a Hyeong Jun Kim, a Pan Seok Kim, b Sung Cheol Yoon*,b and Bumjoon J. Kim*,a a Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon , Korea b Advanced Materials Division, Korea Research Institute of Chemical Technology (KRICT), Daejeon , Korea * Corresponding author: bumjoonkim@kaist.ac.kr phone: Korea Advanced Institute of Science and Technology (KAIST), yoonsch@krict.re.kr phone: , Korea Research Institute of Chemical Technology (KRICT) These authors contributed equally to this work. S1

2 1. Materials and Methods All commercially available reagents were used without further purification. The organic solvents were used as anhydrous solvents. Analytical thin layer chromatography (TLC) was performed using precoated Merck silica gel 60 F254 plates (0.25 mm) with a fluorescent indicator and visualized with UV light (254 and 365 nm). Flash column chromatography was performed on Merck silica gel 60 ( mesh). All 1 H-NMR spectra were recorded at 500 MHz, using CDCl 3 as a solvent, unless otherwise stated. The chemical shifts of all 1 H-NMR spectra are referenced to the residual signal of CDCl 3 (δ 7.26 ppm) with a Bruker 500 MHz NMR instrument. All coupling constants, J, are reported in Hertz (Hz). MALDI-TOF mass spectra were recorded on a Bruker Autoflex III mass spectrometer. Elemental analysis was performed with a ThermoQuest Italia S.P.A model EA1110-FISONS. UV-visible absorption spectra were obtained using a Shimadzu UV-Vis-NIR 3600 spectrophotometer. Cyclic voltammetry (CV) curves were measured with a CHI 600C electrochemical analyzer at room temperature using a conventional three-electrode system (Pt disk working electrode, Pt wire counterelectrode and Ag wire quasi-reference electrode) in 0.1 M tetrabutylammonium tetrafluoroborate (NBu 4 BF 4 ) solution in o-dichlorobenzene at a potential scan rate of 10 mv s -1. The reduction potentials of the acceptor solutions against the Ag quasi-reference electrode were measured and calibrated against a ferrocene/ferrocenium (Fc/Fc + ) redox couple, assuming that the absolute energy level of Fc/Fc + was ev. The molecular size and dipole moment calculations were performed using the Spartan 08 program to compare the molecular structures of the OXCBA derivatives. In particular, we selected a B3LYP density functional theory using a 6-31G * basis set at the equilibrium ground state. 2. Detail experimental procedures General procedure for preparation of α,α -dibromo-o-xylene derivatives as building blocks Solutions of o-xylene derivatives (1 equiv.), N-bromosuccimide (NBS, 2 equiv.) and benzoyl peroxide (BPO, 0.1 equiv.) were refluxed in 1,2-dichloroethane overnight under an Ar atmosphere. After cooling S2

3 to room temperature, the white power in the reaction mixture was filtered, and the filtrate was purified via silica column chromatography (Merck silica gel 60, mesh) with a hexane/ethyl acetate eluent system. 1,2-Bis(bromomethyl)-4-fluorobenzene. 4-Fluoro-1,2-dimethylbenzene (2 g) was reacted with 5.73 g of NBS and 390 mg of BPO in 35 ml of 1,2-dichloroethane. The desired product was purified using silica column chromatography with hexane/ethyl acetate (100/1, v/v) as the eluent, yielding 1630 mg in 35.9% yield. 1 H-NMR (500 MHz, CDCl 3 ) δ: 7.35 (q, J = 2.92, 1H), 7.09 (dd, J 1 = 6.29 and J 2 = 2.69, 1H), (m, 1H), 4.61 (d, J = 11.0, 4H). 2,3-Bis(bromomethyl)naphthalene. 2,3-Dimethylnaphthalene (1 g) was reacted with 2.28 g of NBS and 155 mg of BPO in 20 ml of 1,2- dichloroethane. The desired product was purified using silica column chromatography with hexane as the eluent, yielding 610 mg in 30.4% yield. 1 H-NMR (500 MHz, CDCl 3 ) δ: 7.87 (s, 2H), 7.81 (q, J = 2.86, 2H), 7.51 (q, J = 2.98, 2H), 4.89 (s, 4H). 1-Bromo-4,5-bis(bromomethyl)-2-methoxybenzene. S3

4 4-Methoxy-1,2-dimethylbenzene (5 g) was reacted with 15.7 g of NBS and 890 mg of BPO in 60 ml of 1,2-dichloroethane. The product was purified using silica column chromatography with hexane/ethyl acetate (100/1, v/v) as the eluent, yielding 2.35 g in 17.2% yield. 1 H-NMR (500 MHz, CDCl 3 ) δ: 7.55 (s, 1H), 6.87 (s, 1H), 4.58 (d, J = 10.9, 4H), 3.92 (s, 3H). 1,2-Bis(bromomethyl)-4-nitrobenzene. 1,2-Dimethyl-4-nitrobenzene (3 g) was reacted with 7.42 g of NBS and 509 mg of BPO in 40 ml of 1,2-dichloroethane. The desired product was purified using silica column chromatography with hexane/ethyl acetate (10/1, v/v) as the eluent, yielding 1450 mg in 23.6% yield. 1 H-NMR (500 MHz, CDCl 3 ) δ: 8.25 (d, J = 2.24, 1H), 8.16 (dd, J 1 = 6.12 and J 2 = 2.31, 1H), 7.56 (d, J = 8.42, 1H), 4.66 (d, J = 6.12, 4H). General procedure for preparation of o-xylenyl C 60 bis-adducts(oxcba) derivatives A mixture of C 60 (1 equiv.), building blocks (2 equiv.), potassium iodide (8 equiv.), and 18-crown-6 (8 equiv.) was dissolved in anhydrous o-dichlorobenzene (ODCB) at reflux for 48 h under an Ar atmosphere in the dark. After cooling to room temperature, the reaction mixture was adsorbed on silica gel and purified by flash silica column chromatography (Merck silica gel 60, mesh) with hexane/toluene (v/v) as gradient eluents. The desired product was then concentrated in vacuo and precipitated in excess MeOH to give a brown solid. 4-Fluoro-1,2-xylenyl C 60 bis-adducts. (FXCBA) S4

5 C 60 (1 g) was reacted with 784 mg of 1,2-bis(bromomethyl)-4-fluorobenzene in 150 ml of ODCB. The FXCBA was purified by silica column chromatography with hexane/toluene (6/1, v/v) as the eluent, yielding 250 mg in 18.7% yield. 1 H-NMR (500 MHz, CDCl 3 ) δ: (m, 6H), (m, 8H); elemental analysis for C 76 H 14 F 2 : calculated: C, 94.60; H, 1.46; F, 3.94; found: C, 92.18; H, 1.45 (Purity: 97.4%). MALDI-TOF MS: calculated for C 76 H 14 F ; found: (M + ). Dihydroantracyl-based C 60 bis-adducts. (ACBA) C 60 (0.7 g) was reacted with 610 mg of 2,3-bis(bromomethyl)naphthalene in 100 ml of ODCB. ACBA was purified via silica column chromatography with hexane/toluene (4/1, v/v) as the eluent, yielding 145 mg in 14.5% yield. 1 H-NMR (500 MHz, CDCl 3 ) δ: (m, 12H), (m, 8H); elemental analysis for C 84 H 20 : calculated: C, 98.04; H, 1.96; found: C, 97.04; H, 1.97 (Purity: 99.0%). MALDI-TOF MS: calculated for C 84 H ; found: (M + ). 1-Bromo-2-methoxy-4,5-xylenyl C 60 bis-adducts. (BMXCBA) C 60 (0.5 g) was reacted with 450 mg of 1-bromo-4,5-bis(bromomethyl)-2-methoxybenzene in 70 ml of ODCB. The BMXCBA was purified using silica column chromatography with hexane/toluene (2/1, v/v) S5

6 as the eluent, yielding 214 mg in 27% yield. 1 H-NMR (500 MHz, CDCl 3 ) δ: (m, 4H), (m, 14H); elemental analysis for C 78 H 18 O 2 Br 2 : calculated: C, 81.69; H, 1.58; O, 2.79; Br, 13.94; found: C, 80.84; H, 1.86 (Purity: 99.0%). MALDI-TOF MS: calculated for C 78 H 18 O 2 Br ; found: (M + ). 4-Nitro-1,2-xylenyl C 60 bis-adducts. (NXCBA) C 60 (1 g) was reacted with 860 mg of 1,2-bis(bromomethyl)-4-nitrobenzene in 150 ml of ODCB. The NXCBA was purified via silica column chromatography with hexane/toluene (1/2, v/v) as the eluent, yielding 256 mg in 18.1% yield. 1 H-NMR (500 MHz, CDCl 3 ) δ: (m, 6H), (m, 8H); elemental analysis for C 76 H 14 N 2 O 4 : calculated: C, 89.58; H, 1.38; N, 2,75; O, 6.28; found: C, 88.87; H, 1.45; N, 2.53 (Purity: 99.2%). MALDI-TOF MS: calculated for C 76 H 14 N 2 O ; found: (M + ). S6

7 Figure S H-NMR data of 1,2-bis(bromomethyl)-4-fluorobenzene. Figure S H-NMR data of 2,3-bis(bromomethyl)naphthalene. S7

8 Figure S H-NMR data of 1-bromo-4,5-bis(bromomethyl)-2-methoxybenzene. Figure S H-NMR data of 1,2-bis(bromomethyl)-4-nitrobenzene. S8

9 Figure S H-NMR data of FXCBA. Figure S H-NMR data of ACBA. S9

10 Figure S H-NMR data of BMXCBA. Figure S H-NMR data of NXCBA. S10

11 Figure S2. MALDI-TOF data of OXCBA derivatives. Figure S3. CV curves of OXCBA derivatives in o-dichlorobenzene. S11

12 Absorbance Absorbance OXCBA FXCBA ACBA BMXCBA NXCBA Wavelength (nm) Wavelength (nm) Figure S4. UV-vis absorption spectra of OXCBA derivatives in o-dichlorobenzene (50 µg/ml). PSC Device Fabrications and Measurements Preparation of P3HT: OXCBA derivatives solutions for BHJ PSCs. P3HT (BASF P200) was used as the electron donor, while OXCBA, FXCBA, ACBA, BMXCBA, and NXCBA were used as electron acceptors. Solutions of P3HT, OXCBA, FXCBA, ACBA, BMXCBA, and NXCBA in o-dichlorobenzene (30 mg ml -1 ) were prepared and stirred at 100 C for more than 24 h. The solutions were then passed through a 0.2-µm PTFE syringe filter. Next, blend solutions (donor:acceptor 1:0.6 w/w) composed of P3HT mixed with OXCBA, FXCBA, ACBA, BMXCBA, and NXCBA were prepared with a final P3HT concentration of 15 mg ml -1. Fabrication of normal type PSCs. To investigate the photovoltaic properties of the end functional group-modified OXCBA derivatives in normal BHJ type polymer solar cells, the devices were fabricated using an ITO/PEDOT:PSS/P3HT:Electron acceptor/lif/al structure. ITO-coated glass substrates were subjected to ultrasonication in acetone and 2% Helmanex soap in water, followed by extensive rinsing with S12

13 deionized water, followed by ultrasonication in deionized water and then in isopropyl alcohol. The substrates were then dried for several hours in an oven at 80 C. The ITO substrates were treated with UV-ozone prior to PEDOT:PSS deposition. A filtered dispersion of PEDOT:PSS in water (PH 500) was applied by spin-coating at 2,000 rpm for 30 sec and baking for 20 min at 140 C in air. After application of the PEDOT:PSS layer, all subsequent procedures were performed in a glove box under an N 2 atmosphere. Then, each active blending solution was spin-cast onto an ITO/PEDOT:PSS substrate at 900 rpm for 40 sec. Each P3HT/electron acceptor film was dried, and the final thickness of the films was ~120 nm. The substrates were then placed in an evaporation chamber and held under high vacuum (less than 10-6 Torr) for more than 1 hour before evaporating approximately 0.7 nm of LiF and 100 nm of Al. The configuration of the shadow mask produced four independent devices on each substrate. The active area of the fabricated devices was cm 2. The photovoltaic performance of the devices was characterized using a solar simulator (ABET Technologies) with an air mass (AM) 1.5 G filter. The intensity of the solar simulator was carefully calibrated using an AIST-certified silicon photodiode. The current-voltage behavior was measured using a Keithley 2400 SMU. Fabrication of inverted type PSCs. To investigate the photovoltaic properties of the end functional group-modified OXCBA derivatives in inverted BHJ PSCs, the devices were fabricated using an ITO/ZnO/P3HT:Electron acceptor/pedot:pss/ag structure. The ZnO was prepared using a sol-gel procedure, dissolving zinc acetate dihydrate (Zn(O 2 CCH 3 ) 2 (H 2 O) 2, 99.9%, 1 g) and ethanolamine (HOCH 2 CH 2 NH 2, 99.5%, 0.28 g) in anhydrous 2-methoxy ethanol (CH 3 OCH 2 CH 2 OH, > 99.8%, 10 ml) under vigorous stirring for more than 24 hrs to allow the hydrolysis reaction and aging to proceed. ZnO thin films with a thickness of ~40 nm were prepared by spin-coating the sol-gel precursor solution at 3000 rpm on top of the ITO substrate. The films were heated at 200 C for 1 hr in air. After application of the ZnO layer, all subsequent procedures were performed in a glove box under a N 2 atmosphere. Each active layer blend solution was spin-cast onto an ITO/ZnO substrate at 900 rpm for 40 sec. PEDOT:PSS (VAITRON AI S13

14 4083) was then spin-cast at 4000 rpm on top of the aforementioned layer using X-triton 100 (1~1.5 wt%) as a processing additive to form a smooth layer with a thickness of ~40 nm and then annealed at 120 C in the glove box. Finally, to complete the devices, the top electrode, a ~100 nm Ag film, was thermally evaporated under high vacuum (less than 10-6 Torr). The active area of the fabricated devices was cm 2. The photovoltaic performance of the devices was characterized with a solar simulator (ABET Technologies) with an air mass (AM) 1.5 G filter. The intensity of the solar simulator was carefully calibrated using an AIST-certified silicon photodiode. The current-voltage behavior was measured using a Keithley 2400 SMU. Table S1. Device characteristics of normal type BHJ solar cells composed of P3HT:OXCBA derivatives with various weight ratios at AM 1.5 illumination at 100 mw cm -2. Active layer (w/w) V OC (V) J SC (ma cm -2 ) FF PCE (%) P3HT:OXCBA(1 : 0.6) P3HT:FXCBA(1 : 0.6) P3HT:FXCBA(1 : 0.7) P3HT:FXCBA(1 : 0.8) P3HT:ACBA(1 : 0.6) P3HT:ACBA(1 : 0.7) P3HT:ACBA(1 : 0.8) P3HT:BMXCBA(1 : 0.6) P3HT:BMXCBA(1 : 0.7) P3HT:BMXCBA(1 : 0.8) P3HT:NXCBA(1 : 0.6) P3HT:NXCBA(1 : 0.7) P3HT:NXCBA(1 : 0.8) S14

15 Figure S5. Contact angle of water and glycerol on the P3HT and OXCBA derivatives films. Figure S6. External quantum efficiencies (EQEs) of PSCs based on P3HT:OXCBA derivatives (1:0.6 w/w) devices under AM 1.5 illumination at 100 mw cm -2 S15

16 Table S4. Calculated molecular size and dipole moment of one solubilizing group of OXCBA derivatives. Solubilizing group Volume (Å 3 ) Dipole Moment (D) OXCBA FXCBA ACBA BMXCBA NXCBA S16

17 Figure S7. Air stability measurement of normal and inverted P3HT:OXCBA PSCs; (a) V OC, (b) J SC, and (c) FF. S17