Supporting Information

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1 Supporting Information From Nano to Micrometer Scale: The Role of Anti-Solvent Treatment on the High-Performance Perovskite Solar Cells Sanghyun Paek, Pascal Schouwink, Evangelia-Nefeli Athanasopoulou,, Kyung Taek Cho, Giulia Grancini, Yonghui Lee, Yi Zhang, Francesco Stellacci, Mohammad Khaja Nazeeruddin and Peng Gao General Methods UV-Vis Kinetics study of the perovskite film Unless stated otherwise, steady-state absorption spectra were recorded in transmission mode on a Perkin Elmer Lambda 850 spectrophotometer using a perovskite deposited TiO 2 /FTO glass. Likewise, emission spectra were recorded on a Perkin Elmer Fluorolog spectrofluorometer. Kinetics measurements were carried out as follows: Mesoporous TiO 2 films were deposited on cut FTO glasses and infiltrated with perovskites solution by spin-coating. Simulating the anti-solvent treatment procedure, the samples were then placed vertically in a standard cuvette of 10 mm path length using a Teflon holder. Corresponding anti-solvent was then rapidly injected into the cuvette while the optical absorption at 550 nm was monitored respectively. X-ray diffraction spectroscopy For XRD measurements, the perovskite nanocomposites were deposited on TiO 2 coated FTO classes using the one step deposition procedures. X-ray powder diagrams were recorded on an Bruker D8 Advance equipped with a ceramic tube (Cu anode, λ= Å), and a RTMS X Celerator detector, and operated in BRAGG-BRENTANO geometry. The samples were mounted without further 1

2 modification and rotating at a speed 8 degree per minute (ω) during the measurement, and the automatic divergence slit and beam mask were adjusted to the dimensions of the thin films. A step size of deg was chosen and an acquisition time of up to 7.5min deg -1. A baseline correction was applied to all X-ray powder diagrams to remove the broad diffraction peak arising from the air scattering. Device Fabrication Chemically etched FTO glass (Nippon Sheet Glass) was sequentially cleaned by sonication in a 2 % Helmanex solution, acetone and ethanol for 30 min each, followed by a 15 min UV-ozone treatment. To form a 30-nm thick TiO 2 blocking layer, diluted titanium diisopropoxide bis(acetylacetonate) (TAA) solution (Sigma-Aldrich) in isopropanol was sprayed at 450 C. For the 200 nm mesoporous TiO 2 layer, mesoporous-tio2 layers were made by spin-coating a commercially available TiO2 paste (Dyesol 30NRD). Substrates were baked at 500 o C for 30 min. Then, Li-doping of mesoporous TiO2 is treated by spin coating a 0.1 M solution of Li-TFSI in acetonitrile at 3000 rpm for 10 s followed by another sintering at 500 C for 20 min before the deposition of the perovskite layer. Mixed-perovskite precursor was prepared by mixing 1.15 m PbI 2, 1.10 m FAI, 0.2 m PbBr 2, 0.2 m MABr in a mixed solvent of DMF: DMSO = 4:1 (volume ratio). Perovskite solutions are successively spin-coated in the glovebox as follow: first, 2000 rpm for 10 s with a ramp-up of 200 rpm s 1 ; second, 6000 rpm for 30 s with a ramp-up of 2000 rpm s 1. Various anti-solvents were dropped on the spinning substrate during the second spin-coating step 20 s (trifluorotoluene, 110 ul), 15 s (Chlorobenzene, 100 ul), 15 s (Toluene, 600 ul), 15 s (xylene, 900 ul) and 10 s (diethyl ether, 200 ul), respectively, before the end of the procedure. Then films were annealed at 100 o C for 90 min. The spiro-ometad solution was prepared by dissolving in chlorobenzene at 70 mm. 2

3 tert-butylpyridine (tbp), Tris(2-(1H-pyrazol-1-yl)-4-tert-butylpyridine) cobalt(iii) (FK209) and Tris(bis(trifluoromethylsulfon-yl)imide) (Li-TFSI) were added as additives. Equimolar amounts of additives were added for all hole-transporters: 330 mol% tbp, 50 mol% Li-TFSI from a 1.8M stock solution in acetonitrile and 3 mol% FK209 from a 0.25M stock solution in acetonitrile. The final HTM solutions were spin-coated onto the perovskite layers at 4000rpm for 30s. The gold electrodes were deposited by thermal evaporation of 80 nm gold in high vacuum conditions. Device measurement J-V curves were obtained at a scan rate of 25 mv s -1. All the data are recorded from reverse scan direction. The devices were measured by using a black mask with an active area of 0.16 cm 2. Figure S1. The central area of the film treated by low boiling point anti-solvents like ether or dichloromethane 3

4 Table S1. Physical properties of the bath solvents and shower solvents Solvents Chemical Structure B.P. ( o C) Density a (g/ml) Dipole moment Dielectric constant, ε a DMSO Miscibility DMF Miscibility DMSO D 46.7 Yes Yes DMF D 36.7 Yes Yes DMSO:DMF=4: b Yes Yes Trifluorotoluene D 9.18 Yes Yes Chlorobenzene D 5.62 Yes Yes Toluene D 2.38 Yes Yes CH 3 p-xylene D 2.20 No No CH 3 Ether D 4.33 No Yes Dichloromethane D 9.04 Yes Yes a. 25 o C; b Ch. Wohlfarth. Static Dielectric Constants of Pure Liquids and Binary Liquid Mixtures; Lechner, M. D., Ed.; Landolt-Börnstein - Group IV Physical Chemistry; Springer Berlin Heidelberg: Berlin, Heidelberg, 2008; Vol. 17. Patent WO A2 - Capacitance-based sensing chlorobenzene DIM 4

5 Figure S2. SEM images of perovskite films treated by TFT (a), Toluene (b), Chlorobenzene (c), Xylene (d), ether (e) and without treatment (f). scale bar 2 µm. Table S2. A summary of the fitted time constant values shown in Figure 1 Solvents Equation τ1 (s) τ2 (s) τ3 (s) R 2 TFT y = A1*exp(-x/t1) + y Toluene y = y A1*exp(-(x-x0)/t1) + A2*exp(-(x-x0)/t2) Chlorobenzene y = y A1*exp(-(x-x0)/t1) + A2*exp(-(x-x0)/t2) p-xylene y = y

6 A1*exp(-(x-x0)/t1) + A2*exp(-(x-x0)/t2) Diethyl ether y = A1*exp(-x/t1) + y Dichloromethane y = y A1*exp(-(x-x0)/t1) + A2*exp(-(x-x0)/t2) + A3*exp(-(x-x0)/t3) Figure S3. XRD patterns of perovskite film after A.S.T. and annealing comparing to the simulated (FAPbI 3 ) 0.85 (MAPbBr 3 ) 0.15 powder. 6

7 Table S3. Reduced cubic unit cell volume per formula unit determined from profile fits on experimental data collected after thermal annealing. Perovskite α-fapbi 3 α-fapbi 3 α-fapbi 3 FAPbBr 3 MAPbI 3 Space Group Trigonal, P3m1 Trigonal, P3m1 Cubic, Pm-3m Cubic Pm-3m Tetragonal I4/mcm Volume / f.u.(å 3 ) Ref Perovskite Anti-solvent Volume / f.u.(å 3 ) (FAPbI 3) 0.85(MAPbBr 3) 0.15 w/o A.S.T (7) (FAPbI 3) 0.85(MAPbBr 3) 0.15 DCM (4) (FAPbI 3) 0.85(MAPbBr 3) 0.15 Trifluorotoluene (7) (FAPbI 3) 0.85(MAPbBr 3) 0.15 Toluene (6) (FAPbI 3) 0.85(MAPbBr 3) 0.15 Chlorobenzene (8) MA 0.15FA 0.85PbI (FAPbI 3) 0.85(MAPbBr 3) 0.15 p-xylene (8) (FAPbI 3) 0.85(MAPbBr 3) 0.15 Cubic, P m -3 m (FAPbI 3) 0.85(MAPbBr 3) 0.15 Ether (9) Figure S4. Cross-sections of full devices with the perovskite treated with TFT, Tol, Cb, Xyl, Ether and without A.S.T. scale bar 200 nm. 7

8 Figure S5. Photograph of adding anti-solvents into precursor solution Table S4. RMS statistics based on AFM measurements of five different areas of each film Sample file # area Rms (nm) Sample file # area Rms (nm) TFT Toluene average average st dev st dev Sample file # area Rms (nm) Sample file # area Rms (nm) Reference Xylene

9 average average st dev st dev Sample file # area Rms (nm) Sample file # area Rms (nm) Chlorobenzene Ether average average st dev st dev

10 Dielectric Constant at T = K Ratio of DMF Figure S6. The dependence of dielectric constant with ratio of DMF inside DMSO according to the table in Ch. Wohlfarth. Static Dielectric Constants of Pure Liquids and Binary Liquid Mixtures; Lechner, M. D., Ed.; Landolt-Börnstein - Group IV Physical Chemistry; Springer Berlin Heidelberg: Berlin, Heidelberg, 2008; Vol

11 Figure S7. Hysteresis study of the devices treated with different anti-solvents. 11

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