Supplemental Information. Tailor-Making Low-Cost. Spiro[fluorene-9,9 0 -xanthene]-based. 3D Oligomers for Perovskite Solar Cells

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1 Chem, Volume 2 Supplemental Information Tailor-Making Low-Cost Spiro[fluorene-9,9 0 -xanthene]-based 3D Oligomers for Perovskite Solar Cells Bo Xu, Jinbao Zhang, Yong Hua, Peng Liu, Linqin Wang, Changqing Ruan, Yuanyuan Li, Gerrit Boschloo, Erik M.J. Johansson, Lars Kloo, Anders Hagfeldt, Alex K.-Y. Jen, and Licheng Sun

2 Supporting Information Experimental Section Chemicals: 2-bromo-9-fluorenone, 2,7-dibromo-9-fluorenone, phenol, Methane sulfonic acid, 4-methoxyaniline, 4,4'-dibromo-1,1'-biphenyl, Sodium tert-butoxide, Tri-tert-butylphosphine, Palladium(II) acetate, 1,1,2,2-Tetrachloroethane (TeCA), Chlorobenzene (anhydrous 99.8%), acetonitrile (anhydrous 99.8%), Bis(trifluoromethane)sulfonimide lithium salt (Li-TSFI, 99.95%) and 4-tert-butylpyridine (t-bp, 96%) were purchased from Sigma-Aldrich. PbI2 (purity 99%) and PbBr2 (purity %) were purchased from TCI and Alfa, respectively. FK209 was purchased from Dyenamo. The t-bp was distilled before using; all of the other chemicals were used as received. Spiro-OMeTAD was purchased from Luminescence Technology Corp. Solvents and other chemicals are also commercial available and used as received unless specially stated. Chromatography was performed using silica gel 60Å (35-63 μm). NMR spectra were recorded on a Bruker AVANCE 400 MHz spectrometer. High-resolution MALDI spectra were collected with a Fourier transform-ion cyclotron resonance mass spectrometer instrument (Varian 7.0TFTICR-MS). 1Br-SFX and 2Br-SFX were synthesized according to literatures procedures. Scheme S1. The synthetic route of X54. 1

3 Synthesis of N4,N4'-bis(4-methoxyphenyl)-N4,N4'-di(spiro[fluorene-9,9'-xanthen]-2-yl)- [1,1'-biphenyl]-4,4'-diamine (X54): One-pot reaction was used to synthesized the target molecule, a solution of Pd2(dba)3 (6.2 mg, 0.06 mmol) and DPPF (10.3 mg, 0.1 mmol) in toluene (10 ml) under nitrogen atmosphere was added 4,4'-dibromo-1,1'-biphenyl (312 mg, 1.00 mmol) at room temperature, and the resultant mixture was stirred at that temperature for 10 min. Then, sodium tert-butoxide (240 mg, 2.50 mmol) and 4-methoxyaniline (246 mg, 2.00 mmol) were added to this solution and stirred at 90 C for 8 h. At this time, the starting materials had disappeared as judged by TLC. Then, to solution was added an additional amount of sodium tert-butoxide (240 mg, 2.50 mmol) followed by 1Br-SFX (863.7 mg, 2.10 mmol) and toluene (10 ml). The resultant reaction mixture was stirred at 100 C for overnight. After cooling, the reaction was quenched by adding water, and then extracted with ethyl acetate. The organic layer was dried over anhydrous Na2SO4 and evaporated under vacuum. The collected residue was further purified by silica gel column chromatography (hexane/acetone, v/v, 2:1) to give X54 as yellowish solid (856 mg, yield 81 %). 1 H NMR (400 MHz, d6-dmso, 298 K), δ (ppm): 7.85 (t, J = 8 Hz, 4H), 7.35 (d, J = 8 Hz, 6H), 7.28~7.21 (m, 8H), 7.14 (t, J = 8 Hz, 2H), 7.03~6.83 (m, 20H), 6.68 (s, 2H), 6.42 (d, J = 8 Hz, 4H), 3.71 (s, 6H, OMe). 13 C NMR (400 MHz, C6D6, 298 K), δ (ppm): , , , , , , , , , , , , , , , , , , , , , 54.93, HR-MS (ESI) m/z: [M+1] + calcd for ; found, Synthesis of N2,N7-bis(4-methoxyphenyl)-N2,N7-di(spiro[fluorene-9,9'-xanthen]-2- yl)spiro[fluorene-9,9'-xanthene]-2,7-diamine (X55): The synthesis procedure of X55 was the same as X54 to give X55 as yellow solid (1037 mg, yield 84 %). 1 H NMR (400 MHz, d6-dmso, 298 K), δ (ppm): 7.80 (d, J = 8 Hz, 2H), 7.73 (d, J = 8 Hz, 2H), 7.59 (d, J = 8 Hz, 2H), 7.33~7.19 (m, 12H), 7.11 (t, J = 8 Hz, 4H), 6.97 (d, J = 8 Hz, 2H), 6.88~6.85 (m, 10H), 6.77 (d, J = 8 Hz, 4H), 6.65 (d, J = 8 Hz, 4H), 6.56 (d, J = 8 Hz, 4H), 6.39 (d, J = 8 Hz, 2H), 6.34 (d, J = 8 Hz, 2

4 4H), 3.63 (s, 6H, OMe). 13 C NMR (400 MHz, C6D6, 298 K), δ (ppm): , , , , , , , , , , , , , , , , , , , , , , , , , , , 54.90, 54.85, HR-MS (ESI) m/z: [M+1] + calcd for ; found, Figure S1. 1 H NMR (d6-dmso) spectrum of X54. 3

5 % Figure S2. 13 C NMR (C6D6) spectrum of X54. LJJ-X (1.233) TOF LD e m/z Figure S3. HR-MS spectra of X54. 4

6 Figure S4. 1 H NMR (d6-dmso) spectrum of X55. Figure S5. 13 C NMR (C6D6) spectrum of X55. 5

7 LJJ-X (2.766) TOF LD e % m/z Figure S6. HR-MS spectra of X55. Optical Characterization UV-Vis absorption spectra were recorded on a Lambda 750 UV-Vis spectrophotometer. The fluorescence spectra of dye solutions were recorded on a Cary Eclipse fluorescence spectrophotometer. All samples were measured in a 1 cm cell at room temperature. Electrochemical Measurements Electrochemical experiments were performed with a CH Instruments electrochemical workstation (model 660A) using a conventional three-electrode electrochemical cell. A dichloromethane solution (DCM) containing 0.1 M of tetrabutylammoniunhexafluorophosphate (n-bu4npf6) was introduced as electrolyte, where an Ag/0.01 M AgNO3 electrode (acetonitrile as solvent) was used as the reference electrode and a glassy carbon disk (diameter 3 mm)as the working electrode, a platinum wire as the counter electrode. The cyclovoltammetric scan rates were 50 mv/s. All redox potentials were calibrated 6

8 vs. normal hydrogen electrode (NHE) by the addition of the ferrocene potential. The conversion E(Fc/Fc+) = 630 mv vs NHE. Computational Details In the simulation, optimization and single point energy calculations are performed using the cam-b3lyp and the 6-31G** basis set for all atoms, without any symmetry constraints. All reported calculations were carried out by means of Gaussian 09. The reorganization energy λ, is determined by four energies, (the Nelson four-point method) : λ=e+ * - E++ E * - E Where the E + is the energy of the neutral molecule in the cation symmetry, and the E * is the energy of the cationic molecule in the neutral symmetry; the E+ and E are the optimized energies of the cationic and neutral molecules. Non-adiabatic Marcus theory is used to calculate the charge transfer rate, R: 2π ħ J 2 4πλk B T e (ΔG 0 +λ) 2 4k B T R= where the λ is the reorganization energy, J describes the electronic coupling, and ΔG0 is the free energy between the equilibrium states of the products and reactants. 7

9 Figure S7. Frontier orbitals of X54, X55 and Spiro-OMeTAD. Table S1. Calculated electrochemical properties of X60 and Spiro-OMeTAD. Energy levels are given vs. vacuum. HTMs HOMO (ev) HOMO-1 (ev) LUMO (ev) LUMO+1 (ev) X X Spiro-OMeTAD

10 1.0 X X Spiro-OMeTAD Wavelength (nm) Figure S8. Normalized UV-Visible absorption and photoluminescence of X54, X55 and Spiro-OMeTAD in toluene (10-5 M). Mobility Measurements Hole mobility was investigated by the space-charge-limited current (SCLC) method, which can be described by the following equation: J = 9 8 με 0ε r V 2 d 3 9

11 where J is the current density, μ is the hole mobility, εo is the vacuum permittivity ( F/ m), εr is the dielectric constant of the material (normally taken to approach 3 for organic semiconductors), V is the applied bias, and d is the film thickness. The hole-only devices were fabricated according to the literature procedures. (3) Conductivity Measurements The conductivities of the HTMs were determined by using a two-contact electrical conductivity set-up, which were performed by following published procedures. (3) Glass substrates without conductive layer were carefully cleaned in ultrasonic baths of detergents, deionized water, acetone and ethanol successively. Remaining organic residues were removed with 10 min by airbrushing. A thin layer of nanoporous TiO2 was coated on the glass substrates by spin-coating with a diluted TiO2 paste (Dyesol DSL 18NR-T) with terpineol (1:3, mass ratio). The thickness of the film is ca. 500 nm, as measured with a DekTak profilometer. After sintering the TiO2 film on a hotplate at 500 C for 30 min, the film was cooled to room temperature, before it was subsequently deposited by spin-coating of a solution of HTM in chlorobenzene, whereas the concentrations and additives were the same as in case of photovoltaic devices. Subsequently, a 200 nm thick Ag back contact was deposited onto the organic semiconductor by thermal evaporation in a vacuum chamber with a base pressure of about 10-6 bar, to complete the device fabrication. J-V characteristics were recorded on a Keithley 2400 Semiconductor Characterization System. Device Fabrication Perovskite solar cells: The devices of PSCs were fabricated according to a published method. 1-3 The washing and etching procedures were the same as in case of ssdsc devices. (5) A thin TiO2 blocking layer was deposited on the cleaned FTO glass by spray pyrolysis at 450 C from a precursor solution of 0.2 M titanium diisopropoxide and 2M acetylacetonate in anhydrous 10

12 isopropanol. A mesoporous TiO2 was coated on the substrate by spin coating with a speed of 4500 rpm for 15 s with a ramp of 2000 rpm s -1, from a diluted 30 nm particle paste (Dyesol) in ethanol, the weight ratio of TiO2 (Dyesol paste) and ethanol is 5.5:1. Subsequently, the substrate was immediately dried on a hotplate at 80 C, and then the substrates were sintered at 500 C for 20 min. The perovskite film was deposited by spin coating onto the TiO2 substrate. The perovskite layer was deposited by spin coating the perovskite precursor solution in one-step, which was prepared by mixing of the formamidinium iodide (FAI), lead iodide (PbI2), methylamonium bromide (MABr) and lead bromide (PbBr2) in a mixed solvent of DMF and DMSO solution (volume ratio 4:1) with the molar concentration of 1.35M Pb 2+ (PbI2 and PbBr2). The molar ratio of PbI2/PbBr2=85/15, PbI2/FAI=1.05, PbBr2/MABr=1/1. The spin coating procedure was done in an Argon flowing glovebox, first 2000 rpm for 10 s with a ramp of 200 rpm s -1, second 4000 rpm for 30 s with a ramp of 2000 rpm s µl chlorobenzene was dropped on the spinning substrate during the second spincoating step 20 s before the end of the procedure. The substrate was then heated at 100 C for 90 min on a hotplate. After cooling down to room temperature, HTM was subsequently deposited on the top of the perovskite layer by spin coating at 4000 rpm for 20 s. The HTM solutions were prepared by dissolving the HTM in chlorobenzene at a concentration of 70 mm, with the addition of 30 mm LiTFSI (from a stock solution in acetonitrile with concentration of 1.0 M), 200 mm of t-bp (from a stock solution in chlorobenzene with concentration of 1.0 M) and 1.8 mm FK209 () (from a stock solution in acetonitrile with concentration of 0.5 M). The HTM solution was dripped on the perovskite electrode and then followed by spin-coating for 30 s with 3000 rpm. All of the HTM solutions were prepared in glove box under nitrogen atmosphere; chlorobenzene and acetonitrile were deaerated by bubbling with dry nitrogen for half hours before introducing into glove box environment. Finally, 80 nm of gold was deposited by thermal evaporation using a shadow mask to pattern the electrodes. 11

13 Device Characterization Current-Voltage characteristics were recorded by applying an external potential bias to the cell while recording the generated photocurrent with a Keithley model 2400 digital source meter. The light source was a 300 W collimated xenon lamp (Newport) calibrated with the light intensity of 100 mw cm -2 at AM 1.5 G solar light condition by a certified silicon solar cell (Fraunhofer ISE). IPCE spectra were recorded on a computer-controlled setup comprised of a xenon lamp (Spectral Products ASB-XE-175), a monochromator (Spectral Products CM110) and a Keithley multimeter (Model 2700). The setup was calibrated with a certified silicon solar cell (Fraunhofer ISE) prior to measurements. The prepared ssdsc samples were masked during the measurement with an aperture area of cm 2 (diameter 4 mm) exposed under illumination. The prepared PSC samples were masked during the measurement with an aperture area of 0.2 cm 2 exposed under illumination The transient photocurrent decay was measured with the complete solar cell and the details in the measurements can be found in our previous publications. 1,2,4,5 PL and Steady-state PL The PL was measured by using FTO/TiO2/Perovskite with and without HTM layer. An excitation wavelength of 460 nm was used. The angle between the incident light and the substrate was fixed at 60 o. Scanning Electron Microscopy (SEM) The surface morphology of samples was characterized using SEM (Zeiss MERLIN Field Emission SEM, Germany). 12

14 Figure S9. The solubility of X54 and X55 in chlorobenzene at the same concentration (70 mg/ml). Figure S10. J-V characteristics of X54, X55 and Spiro-OMeTAD based hole-only devices with dopant. 13

15 Figure S11. The J-V characteristics of the best PSCs using X55 as HTM under different scan conditions. Figure S12. The derived contact angles between X54, X55 and Spiro-OMeTAD-based films and water. 14

16 Figure S13. The stability of X55 and Spiro-OMeTAD-based devices (without encapsulation) at ambient condition with ~60% air humidity under different temperatures. References (1) Zhang, J.; Hua, Y.; Xu, B.; Yang, L.; Liu, P.; Johansson, M. B.; Vlachopoulos, N.; Kloo, L.; Boschloo, G.; Johansson, E. M. J.; Sun, L.; Hagfeldt, A. Adv Energy Mater 2016, 6, (2) Zhang, J. B.; Xu, B.; Johansson, M. B.; Hadadian, M.; Baena, J. P. C.; Liu, P.; Hua, Y.; Vlachopoulos, N.; Johansson, E. M. J.; Boschloo, G.; Sun, L.; Hagfeldt, A. Adv Energy Mater 2016, 6. (3) Zhang, J.; Xu, B.; Johansson, M. B.; Vlachopoulos, N.; Boschloo, G.; Sun, L.; Johansson, E. M.; Hagfeldt, A. ACS Nano 2016, 10, (4) Yu, Z.; Sun, L. Adv Energy Mater 2015, 5, 5, (5) Zhang, J. B.; Vlachopoulos, N.; Jouini, M.; Johansson, M. B.; Zhang, X. L.; Nazeeruddin, M. K.; Boschloo, G.; Johansson, E. M. J.; Hagfeldt, A. Nano Energy 2016, 19,