Supporting Information Chemicals Synthesis Phenyl-C61-butyric acid Phenyl-C61-buryric acid 1H, 1H-Pentadecafluoro-1-octyl ester (F-PCBM)

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1 Supporting Information Self-Organized Buffer Layers in Organic Solar Cells By Qingshuo Wei, Takeshi Nishizawa, Keisuke Tajima*, and Kazuhito Hashimoto* Chemicals Acetic acid (CH 3 COOH), hydrochloric acid (HCl), thionyl chloride (SOCl 2 ), carbon disulfide (CS 2 ) and toluene were purchased from Wako Pure Chemicals Industries, Ltd., Japan. 1H, 1H-Pentadecafluoro-1-octanol (CF 3 (CF 2 ) 6 CH 2 OH) was purchased from Tokyo Chemical Industry Co. Ltd., Japan. Chlorobenzene (C 6 H 5 Cl, 99.8%) was purchased from Aldrich. Poly-3-hexylthiophene (P3HT) was synthesized by McCullough method. PCBM was purchased from Frontier Carbon Corp., Japan. ITOcoated glass (Rs = 10 Ω/square) was purchased from Kuramoto, Japan. Synthesis Phenyl-C 61 -butyric acid Acetic acid (150 ml) and HCl (60 ml) were added to a solution of PCBM (Compound 1, 1.0 g, 1.1 mmol) in 150 ml of toluene, and the mixed solution was heated to reflux for 18 h. After the solution was evaporated, the crude product was treated with methanol, centrifuged to collect the suspension. This procedure was repeated with diethyl ether, toluene, and twice with diethyl ether, to yield 0.62 g (63%) of P2. 1 H NMR (400 MHz, CDCl 3 ), δ (ppm): 7.66 (d, J = 7.2 Hz, 2H), (m, 2H), (m, 1H), (m, 2H), 2.67 (t, J = 7.2 Hz, 2H), (m, 2H). MALDI TOF-MS m / z: (calc.), (found). Phenyl-C 61 -buryric acid 1H, 1H-Pentadecafluoro-1-octyl ester (F-PCBM) Thienyl chloride (3 ml, 41.3 mmol) was added to a solution of P2 (400 mg, mmol) in 70 ml of freshly distilled CS 2, and the solution was heated to reflux for 24 h. After all the volatile components were removed in vacuo, sodium hydride (28 mg, 1.17 mmol), toluene (80 ml), and 1H, 1H-Pentadecafluoro-1-octanol (800 mg, 2.0 mmol) dissolved in 15 ml of toluene were added to the residue (P3). The mixed solution was stirred for 2 days, and then the solution was evaporated. The product was purified by silica column chromatography eluting with ethyl acetate/hexanes (1:1) at first, and then eluting with chloroform/hexanes (1:1) yielding 184 mg (35%) of P4. 1

2 1 H NMR (500 MHz, CDCl 3 ), δ (ppm): (m, 2H), (m, 2H), (m, 1H), 4.60 (t, J = 13.8 Hz, 2H), (m, 2H), 2.63 (t, J = 7.6 Hz, 2H), (m, 2H). 19 F NMR (500 MHz, CDCl 3 ), δ (ppm): (d, 3F), (s, 2F), (s, 4F), (s, 2F), (s, 2F), (s, 2F). 13 C NMR (500 MHz, CDCl 3 ), δ (CDCl 3 = ppm): , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , 79.73, 51.61, 33.50, 33.41, High-resolution MALDI-TOF-MS m / z: , , , , (calc.), , , , , (found). NMR and MALDI-TOF-MS Spectra of F-PCBM 1 H-NMR and 13 C-NMR spectra were measured by OXFORD Superconducting magnet system (500 MHz). 19 F-NMR spectra were recorded on JEOL JNM-ECP500 spectrometer. MALDI-TOF-MS spectra were measured with dithranol as a matrix on Applied Biosystems BioSpectrometry Workstation model Voyager-DE STR spectrometer. High-resolution spectra were measured with Cyano-4-hydroxycinnamic acid as a matrix and calibrated by using Angiotensin II Human ( ) and Substance P ( ) as the internal standards. 2

3 ppm Figure S1 1 H-NMR spectrum of F-PCBM. 3

4 ppm Figure S2 13 C-NMR spectrum of F-PCBM. 4

5 ppm Figure S3 19 F-NMR spectrum of F-PCBM. 5

6 a Counts (a.u.) Mass (m/z) b Counts (a.u.) Mass (m/z) Figure S4 a) High-resolution MALDI-TOF-MS spectrum of F-PCBM and b) blowup of the molecular ion region. 6

7 a b c d Figure S5 AFM height images (1μm 1 μm) of a) P3HT: PCBM: F-PCBM and b) P3HT: PCBM as-cast films, and of c) P3HT: PCBM: F-PCBM and d) P3HT: PCBM: F-PCBM films after annealed at 150 C for 5mins. 7

8 [18, 24, 25] Estimation of Interface Dipole from Calculations The change in work function with monolayer dipole molecule can be written as: Δ φ = N[ μmol / ε mol + μbond / ε bond ] where Δφ is the change in surface potentials, N is the surface density of molecules, μ mol is the dipole moment of an individual molecule in the thin film projected onto the axis normal to the surface, ε mol is the static dielectric constant of the molecular layer, and μ bond /ε bond is the effective dipole moment of the bond. F-PCBM was assumed to form a uniform monolayer on the PCBM film with the CF 3 CF 2 CF 2 CF 2 CF 2 CF 2 CF 2 CH 2 groups exposed to the air, as shown in Figure S6. The effective dipole moment of the bond was ignored here due to nonpolarity C-C bond. If the F- PCBM densely packed on the surface, the areal density N was calculated to be m -2. Dielectric constant was taken from poly(tetrafluoroethylene). [18] The dipole moment of the molecule was calculated by using Gaussian 98 according to previous reports. [25] N: m -2 μ mol : 3.67 Debyes ε mol : 2.1 μ bond : 0 Δφ: 0.36 ev Figure S6 Schematic representation of PCBM: F-PCBM blended film used for the calculation (top) and molecular structure of F-PCBM (bottom). 8