Hassan_et_al-Advanced_Materials.sup-1

Copyright WILEY‐VCH Verlag GmbH & Co. KGaA, 69469 Weinheim, Germany, 2015.Supporting Informationfor Adv. Mater., DOI: 10.1002/adma.201503461Structure-Tuned Lead Halide Perovskite Nanocrystals Yasser Hassan, Yin Song, Ryan D. Pensack, Ahmed I. Abdelrahman, Yoichi Kobayashi, Mitchell A. Winnik, and Gregory D. Scholes*Supporting InformationStructure-Tuned Lead Halide Perovskite NanocrystalsYasser Hassan, Yin Song, Ryan D. Pensack, Ahmed I. Abdelrahman, Yoichi Kobayashi, Mitchell A. Winnik and Gregory D. ScholesContentsI. Additional experimental details (2)FluorimeteryFluorescence quantum yield (2)II. Photographs of lead iodide and corresponding perovskite nanocrystals (3)Transmission Electron Microscopy of PbI2 NCs (4)Transmission Electron Microscopy (4)Experimental Selected Area Electron Diffraction (SAED) (5)Simulated SAED (5)Ligand and solvent effects on the optical properties of perovskite NCs (7)Details of powder X-ray diffraction (PXRD) measurements including samplepreparation (8)X–ray photoelectron spectroscopy (XPS) (10)Time-Correlated Single Photon Counting Measurements for 2D Perovskite NCs (n=3) (12)References (13)Additional experimental details1A.Fluorimetry. Fluorescence spectra were obtained and fluorescence quantum yield (FQY)measurements were performed on a PTI Quantum Master Fluorimeter (PhotonTechnology International, Inc., Birmingham, NJ) consisting of a Xenon lamp, a double excitation monochromator, a single emission monochromator, and a Hamamatsu R928 photomultiplier tube. Slit widths were set to 1.2 mm for both excitation and emission monochromators for measurements of the perovskite nanocrystal fluorescence spectra.Typical scan parameters were 2 nm steps and 1.0 s integration time.B.Fluorescence quantum yield. The relative fluorescence quantum yield measurement wascarried out on solution with a maximum O.D. of <0.05 in a 1 cm path length quartz cell (Starna Cells, Inc., Atascadero, CA). Cresyl violet in methanol (FQY=0.54)[1] was used asa fluorescence quantum yield standard. Cresyl violet was chosen, in particular, as itsfluorescence spectrum exhibits significant overlap with that of the perovskite nanocrystal photoluminescence (i.e., specifically n=3 perovskite). Spectranalyzed methanol (Fischer) was used as the solvent for cresyl violet. A mixture of spectrophotometric-gradechloroform and toluene was used as the solvent for the perovskite nanocrystals. Theexcitation wavelength was set at 530 nm. The slit widths were chosen to maximize the signal for the dye, while staying within the linear range of the detector response. The dye and perovskite nanocrystal samples were excited at the same wavelength to ensure that each were exposed to the same intensity of light. The solutions were not deoxygenated prior to measurements. Cresyl violet in air- and nitrogen-saturated solutions exhibitidentical fluorescence intensities [1]; loss of the volatile methyl ammonium iodidecomponent within the perovskite nanocrystal suspension caused the perovskitenanocrystals to degrade under nitrogen-saturation.2I.Photographs of lead iodide and corresponding perovskite nanocrystalsComparing the solution color before and after the treatment of the PbI2 NCs shows a change from a pale yellow to a red solution, the latter being representative of the color of the 2D lead iodide perovskite NCs (Fig. S1).Figure S1. Photograph of a colloidal lead iodide NC suspension and the corresponding 2D organo-lead iodide perovskite NCs. a, Photograph of a colloidal lead iodide NC suspension in toluene and the corresponding 2D organo-lead iodide perovskite (n= 3) NCs in mixture of toluene: chloroform (2:1) under exposure to ambient and UV light. (b) Photograph of a colloidal 2D perovskite (n=3) suspension in a mixture of chloroform and toluene.3II.Transmission Electron Microscopy of PbI2 NCsA.Transmission Electron MicroscopyFigure S2.Transmission Electron Microscopy of PbI2 NCs.a,TEM images of PbI2 NCs prepared at 160 o C. b,c, High-resolution electron microscopy (HRTEM) of the PbI2 NCs. d, Fast Fourier transform (FFT) of the HRTEM image showing the (101), (102), (111) and (004) lattice fringes.4B.Experimental Selected Area Electron Diffraction (SAED)Selective Area Electron Diffraction (SAED) patterns for a collection of PbI2 nanocrystals deposited on a carbon grid (Figure S3) were obtained using transmission electron microscopy (TEM; JEOL 2010 at 200 kV).Figure S3. Experimental selected area electron diffraction (SAED) patterns of PbI2 NCs.SAED image of PbI2 NCs of size 10 nm prepared at 200 o C, 30 minutes growth.C.Simulated SAEDElectron diffraction patterns were simulated with open-source software GDIS[2] andDiffraction Ring Profiler[3] using the space group information of the hexagonal phase of PbI2 (PDF card no 43-1484). The latter software package integrates the SAED ring patternintensities to accurately calculate the center point of each ring. The simulated SAED pattern can be found in Figure Fig S4.5Figure S4. Experimental and simulated selected area electron diffraction (SAED) patterns of PbI2 NCs. a, Comparison of the SAED of PbI2 NCs and the simulated XRD patterns of the PbI2 hexagonal structure (PDF card no. 43-1484). b, Integrated SAED and simulated XRD patterns of PbI2 NCs. The simulation of the SAED was performed using open-source software Diffraction Ring Profiler.6III.Ligand and solvent effects on the optical properties of perovskite NCsFigure S5. Absorption spectra of perovskite NCs synthesized with different ligands and solvent mixture ratios. a, Absorption spectra of perovskite NCs synthesized with butyl-, octyl-, and olelyl-ammonium ligands. b, Absorption spectra of perovskite NCs synthesized with olelylammonium ligand with different solvent mixture ratios, i.e., toluene (T) to chloroform (CF) = 2:1, 1:1 and 1:1.5 v/v ratio.7IV.Details of powder X-ray diffraction (XRD) measurements including sample preparationX-ray patterns for phase purity were recorded on a Rigaku MiniFlex Benchtop X-ray diffractometer (equipped with Cu Kα X-ray tube) operating at 600 watts (tube voltage 40 kV and 15 mA) with a time per step of 3 s at range of = 0–60 degree. Samples were rotated during data collection.In order to study the effect of PbI2 sample preparation method on the PXRD, we prepared films by two different methods: (i) methanol treatment method and (ii) spin coating without methanol treatment.(i) Methanol treatment methodPbI2 NCs were purified by iteratively precipitating in methanol and subsequently re-dissolving in toluene in order to remove excess and weakly bound surface ligands (Figure S6a).(ii) Spin coatingIn this method the PbI2 NC solution in hexane, toluene or chloroform were spin coated on a silicon substrate. The thickness of the deposited films was 10-20 nm. The film was dried by flushing with nitrogen gas prior to the XRD measurements (Figure S6b).Perovskite NCs did not undergo the removal of excessive ligands; i.e. the diffractogram of the perovskite NCs was obtained on a powder of nanocrystals that had been prepared by evaporating the toluene:chloroform solution after deposition on a silicon substrate at room temperature from a concentrated NCs colloidal solution. The diffractogram of the 2D perovskite NCs (in case of n=1 and 2) was obtained on a powder of nanocrystals while the diffractogram of the 2D perovskite NCs (n=3) was performed on film prepared by spin coating.Calculating the d-spacing from XRD peaks:8From Braggs’ law, we calculated the interplanar distance, i.e. the d-spacing.2θhkl=2arcSin (λ2d hkl ) , then d hkl =(h2a2+k2b2+l2c2)−12where a, b, and c are the cell parameters, d hkl is the interplanar distance.For plane (002); the d002=c/2 or c=2*d002Figure S6 shows the powder X-ray diffraction (XRD) pattern of the 3D organo-lead halide perovskite NCs (CH3NH3PbI3) prepared by mixing the PbI2 NCs with excess MAI and spin coated on a glass substrate. This substrate was treated by heating at 70-100 o C for 5 minutes before undergoes measurements. This heating lead to the crystal phase transformation to the three dimensional lattice.Figure S6a (blue line) shows strong reflection peaks at 14.03o, 28.13o, 28.3o and 31.67o, corresponding to the (002), (004), (200) and (222) planes, respectively, indicate high crystallinity of a typical diffraction pattern of a tetragonal perovskite phase (space group I4/mcm)[4]. The FWHM of the XRD peaks indicate that the NCs aggregated upon evaporation to form a larger particle size (several tens nanometer). The strong diffraction peaks at 2θ =19.55 and 29.57 o (starred) can be attributed to unreacted excess MAI precursor[5]. The absence of the PbI2 peak in the perovskite XRD spectrum suggests complete conversion of PbI2 NCs to perovskite which is in agreement with absorption spectrum of perovskite in Figure 2b.9Figure S6. Powder X -ray diffraction (XRD) measurements of PbI 2 and the corresponding 2D organo -lead iodide perovskite NCs. a , X–ray diffractogram of PbI 2 after washing by methanol (red) and after the transformation to lead halide perovskite (blue). The blue line indicates the XRD results for perovskite powder , which was deposited on a silicon substrate at room temperature from a concentrated colloidal NCs solution without any further treatment, while PbI 2 NCs were precipitated using a methanol/heptane mixture before centrifugation and collection for measurements. Perovskite reflection peaks are assigned to the tetragonalperovskite crystal lattice except the peaks at 19 and 29 degrees coming from the unreacted precursors. * denote diffraction peaks corresponding to unreacted precursors and not from the perovskite. The plot displays the X–ray intensity as a function of twice the diffraction angle (2 ). b , X–ray diffractogram of PbI 2 films deposited by spin coating without washing (black line) and the calculated XRD spectra of PbI 2 hexagonal phase (red line).baV.X–ray photoelectron spectroscopy (XPS)The spin-orbit splitting between the Pb 4f7/2 and Pb 4f5/2 core levels and between I 3d5/2 and I 3d3/2 core levels are 4.86 and 11.5 eV, respectively; which are similar to values previously reported[6, 7] for lead halide perovskites. In order to determine the stoichiometry and chemical environments present in the NCs, the peaks were fitted according to a Gaussian-Lorentzian peak shape along with a ‘Smart’ background. Quantifying the values of the area under the peaks, we calculated the ratio of Pb:I and found it to be 3:10 corresponding to 2D (n= 3)OL2(CH3NH3)2[Pb3I10] perovskite (where OL = oleylamine) and molar ratio 2:7 in case of 2D (n=2) OL2CH3NH3[Pb2I7] and these results are consistent in all samples measured. In the case of iodide peaks of the perovskite NCs (n=3), it was found when we used the Gaussian fitting the presence of a small peak at 617 eV (4 % of the total iodide in the sample) which corresponds to the iodide bond in the excess of unreacted methyl ammonium iodide[7].Figure S7.Representative X–ray photoelectron spectroscopy (XPS) analysis of a, Pb 4f core level and b, I 3d core level of 2 D perovskite film deposited from evaporated NCs solution. XPS showing the Pb(II) 4f7/2 and 4f5/2 transitions with a binding energy of 137.8 eV and 142.7 eV respectively with no metallic Pb component observed, and I 3d5/2 and 3d3/2 transitions with a binding energy of 619.28 and 630.78 eV, respectively. c and d, Gaussian-Lorentzian peak shape fitting along with a ‘Smart’ background of Pb 4f core level and I 3d core level of 2 D perovskite NCs.Figure S8. X–ray photoelectron spectroscopy (XPS) analysis of PbI2 NCs. a, Gaussian-Lorentzian peak shape fitting along with a ‘Smart’ background of a, Pb 4f core level and b, I 3d core level of PbI2 NCs film deposited from evaporated NCs solution. XPS showing the Pb(II) 4f7/2 and 4f5/2 transitions with a binding energy of 138.5 eV and 143.42 eV respectively with no metallic Pb component observed, and I 3d5/2 and 3d3/2 transitions with a binding energy of 619.18 and 630.68 eV, respectively.VI.Time-Correlated Single Photon Counting Measurements for 2D Perovskite (n=3)TCSPC measurements of the 2D perovskite (n=3)nanocrystal suspension. The excitation wavelength was 374 nm and the emission wavelength was 646 nm. Overlaying the data (black) is a biexponential fit (red) with time constants of 14 and 46 ns.Table S1. Amplitudes and Time Constants Obtained from Biexponential Fit to TCSPC Measurements on 2D Perovskite (n=3) Nanocrystal SuspensionVII.References[1] D. Magde, J. H. Brannon, T. L. Cremers, J. Olmsted, The Journal of Physical Chemistry 1979, 83, 696.[2]S. Fleming, A. Rohl, Zeitschrift fur Kristallographie 2005, 220, 580.[3]L. Zhang, C. M. B. Holt, E. J. Luber, B. C. Olsen, H. Wang, M. Danaie, X. Cui, X. Tan, V. W. Lui, W. P. 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