Supporting Information for. Synthesis of Perfectly Oriented and Micrometer-Sized MAPbBr 3. Perovskite Crystals for Thin Film Photovoltaic Applications

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1 Supporting Information for Synthesis of Perfectly Oriented and Micrometer-Sized MAPbBr 3 Perovskite Crystals for Thin Film Photovoltaic Applications Nadja Giesbrecht, 1 Johannes Schlipf, 2 Lukas Oesinghaus, 2 Andreas Binek, 1 Thomas Bein, 1 Peter Müller-Buschbaum, 2, * Pablo Docampo 1, * 1 Department of Chemistry and Center for NanoScience (CeNS), University of Munich (LMU), Butenandtstr. 11, Munich, Germany 2 Lehrstuhl für Funktionelle Materialien, Physik-Department, Technische Universität München, James-Franck-Str. 1, Garching, Germany AUTHOR INFORMATION Corresponding Author * Pablo.docampo@cup.lmu.de. * muellerb@ph.tum.de. Experimental Device Fabrication Substrate preparation: Fluorine-doped tin oxide (FTO, Pilkington, 7 Ω -1 ) substrates or indium-doped tin oxide (ITO, Zhuhai Kaivo Optoelectronic Technology Co., Ltd., <15 Ω -1 ) were etched with 2 M HCl and zinc powder and cleaned in 2 % Hallmanex detergent, acetone

2 and ethanol. The TiO 2 layer was deposited via a sol-gel approach where a solution containing 0.23 M titanium isopropoxide (Sigma Aldrich, %) and M HCl in isopropanol was spin-coated on FTO or ITO at 2000 rpm for 30 s and annealed at 150 C for 10 min and for 45 min at 400 C for the ITO and at 500 C for the FTO in ambient air conditions. Perovskite deposition: CH 3 NH 3 Br was synthesized by reacting 8 ml of hydrobromic acid (48 vol% in water) with 24 ml of methylamine (33 vol% in methanol, Sigma-Aldrich) in ethanol in a round-bottom flask at room temperature for 1 h. To recover the precipitates, solvent evaporation at 60 C at a pressure of 200 mbar was used and the products were recrystallized in ethanol, filtered and dried with diethylether and under vacuum afterwards. BD: A 1.2 M solution of the perovskite precursors PbBr 2 and MABr (1:1 ratio) was prepared in a solvent mixture of γ-butyrolactone and dimethylsulfoxide in a 7:3 ratio. The precursor solution was deposited in a 3-step spin-coating program. The first step of the program was at 500 rpm for 5s, the second step was at 1000 rpm for 40 s and the third step was at 5000 rpm for 50 s. At the beginning of the last step toluene was dripped on the substrate. Afterwards the films were annealed at 100 C for 10 min. VASP: In the vapor-assisted-solution process first the lead bromide precursor layer was deposited. The PbBr 2 was dissolved in DMF (a 1 M solution) and preheated together with the substrates at 60 C before spin-coating the layer at 3000 rpm for 15 s. Afterwards the PbBr 2 was dried at 60 C for 10 min and converted in a closed vial to the perovskite in MABr vapor for 2 hours at 150 C.

3 CSD: The perovskite layer was deposited at room temperature kept substrate via dynamically spin-coating 50 µl solution (1.5 Pb(Ac) M MABr in DMF) per 9 cm 2 of substrate dimension at 5000 rpm for 3 min. The samples were then annealed at 100 C for 2 min with a glass lid covering the substrate in order to avoid defects caused by gas circulation. Electrode deposition: On top of the perovskite a 100 mg/ml solution of spiro-ometad in chlorobenzene was spincoated at 1500 rpm for 45 s and a second step at 2000 rpm for 5 s. Finally a 40 nm thick Au (Sigma-Aldrich) counter electrode was thermally evaporated under high vacuum conditions (<10-6 mbar) through a metal aperture leading to devices in the range of 0.10 cm 2. The active area was determined with a cm 2 metal aperture. Characterization X-ray diffraction: 2 ϑ scans were obtained from samples of perovskite deposited on TiO 2 -coated FTO or ITO glass using an X-ray diffractometer (Bruker D8 Discover). GIWAXS-Measurement: GIWAXS measurements were performed using a Ganesha 300XL SAXS-WAXS with an 8 kev Cu-K α X-ray source. The incident angle of 0.4 and the sample-detector distance (SDD) of approximately 106 mm were chosen according to the material properties. The exact value of the SDD was determined for each measurement by careful calibration using XRD data. For data evaluation we used the software GIXSGUI by the Advanced Photon Source (APS) of the

4 Argonne National Laboratory, USA. 1 The applied corrections include the solid angle correction, the efficiency correction and the polarization correction. 2, 3 SEM: A scanning microscope (JSM-6500F) was used to acquire SEM images of perovskite layers prepared on TiO 2 -coated FTO/ ITO glass. Light absorption: The absorptance of the perovskite films on TiO 2 -coated ITO glass was measured with a Lambda 1050 UV/Vis spectrometer (Perkin Elmer) using an integrating sphere. Photoluminescence: Steady-state and time-correlated single photon counting measurements of the perovskite films coated on non-conductive glass were performed with a Fluotime 300 Spectrofluorometer (Picoquant GmbH); the excitation wavelength was fixed to 510 nm with a pump fluence of ~0.3 µjcm -2 and the emission was monitored at the maximum at 550 nm, the maximum intensity of the steady state photo emission. Device Characterization: Photovoltaic device performance was measured with a Keithley 2400 sourcemeter in air at 25 C under illumination by an Newport Oriel Sol2A solar simulator, which was calibrated to 100 mw/cm -2 with a Fraunhofer ISE certified silicon cell with a mismatch factor of The active area of the solar cell was defined with a square metal aperture mask of cm 2.

5 Fig. SI 1: Schematic illustration of the perovskite-layer synthesis approach via evaporation; first: PbBr 2 was deposited via spin-coating; second: the PbBr 2 film was dried on a hotplate; third: conversion of the PbBr 2 to the perovskite in a MABr vapor.

6 Fig. SI 2: SEM images of MAPbBr 3 perovskite films deposited via the state-of-the-art BD method; a,b,c) top view on a film prepared on ITO, d) cross-sectional image of a solar cell device prepared on ITO, e) J-V curve under AM 1.5 solar irradiation conditions of the best performing device, f) XRD pattern normalized to the reflex at 2 ϑ = 14.9.

7 Fig. SI 3: a) SEM images of MAPbBr 3 perovskite films deposited via CSD, b) SEM top-view of MAPbBr 3 perovskite-film deposited by spin-coating from lead acetate precursor with a short spin-coating duration of 30 s, c) SEM top view of FAPbBr 3 deposited with the CSD method on TiO 2 /ITO coated glass.

8 Fig. SI 4: SEM cross-sectional images of MAPbBr 3 perovskite solar cells in the configuration ITO/TiO 2 /MAPbBr 3 /Spiro-OMeTAD/ Au.

9 Fig. SI 5: SEM top views of MAPbBr3 perovskite films deposited via CSD; a, b) films deposited with an excess of perovskite solution, c, d) films deposited in a MeOH containing environment in the glove-box.

10 Fig. SI 6: a) Absorptance of MAPbBr 3 prepared via VASP or spin-coating from lead acetate precursor, b) PL decay curves for MAPbBr 3 prepared via VASP or spin-coating from lead acetate precursor. The samples were illuminated at 510 nm with a pump fluence of ~0.3 µjcm -2 ; the emission was monitored at the maximum of PL emission at nm for CSD and 540 nm for VASP; c) PL emission.

11 Fig. SI 7: Distribution of device performance data of 20 devices with perovskite films prepared via VASP or spin-coating from a lead acetate precursor (CSD), a) open circuit voltage, b) fill factor, c) forward and reverse scanning results for solar cells employing MAPbBr 3 derived from CSD.

12 Fig. SI 8: a) SEM top views of MAPbBr 3 perovskite films deposited via VASP, b) SEM top views of MAPbBr 3 perovskite films deposited via CSD on FTO, c) XRD pattern normalized to the reflex at 2 ϑ = 14.9.

13 Fig. SI 9: Distribution of device performance data of 45 devices with perovskite films prepared via spin-coating from a lead acetate precursor (CSD) with an FTO- or ITO-coated substrate, a) short circuit current output, b) fill factor, c) open circuit voltage, d) power conversion efficiencies. References: (1) Jiang, Z. GIXSGUI: a MATLAB Toolbox for Grazing-Incidence X-Ray Scattering Data Visualization and Reduction, and Indexing of Buried Three-Dimensional Periodic Nanostructured Films J. Appl. Crystallogr. 2015, 48,

14 (2) Schleputz, C. M.; Herger, R.; Willmott, P. R.; Patterson, B. D.; Bunk, O.; Bronnimann, C.; Henrich, B.; Hulsen, G.; Eikenberry, E. F. Improved Data Acquisition in Grazing- Incidence X-Ray Scattering Experiments Using a Pixel Detector. Acta Crystallographica Section A 2005, 61, (3) Chen, W.; Nikiforov, M. P.; Darling, S. B. Morphology Characterization in Organic and Hybrid Solar Cells. Energy Environ. Sci. 2012, 5,