Supporting Information

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1 Supporting Information Band Gap Tuning of CH 3 NH 3 Pb(Br 1-x Cl x ) 3 Hybrid Perovskite for Blue Electroluminescence Naresh K. Kumawat 1, Amrita Dey 1, Aravindh Kumar 2, Sreelekha P. Gopinathan 3, K. L. Narasimhan 2 and Dinesh Kabra*,1 1 Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai, India. Pin Code Department of Electrical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, India. Pin Code Centre for Research in Nanotechnology & Science (CRNTS), Indian Institute of Technology Bombay, Powai, Mumbai, India. Pin Code 4000 * (dkabra@iitb.ac.in) This file included following information: Material synthesis and methods Figures S1 to S5 1

2 Materials and methods Materials Synthesis Methylammonium chloride (CH 3 NH 3 Cl) precursor: We have used methylamine (CH 3 NH 2 ) 33 wt% in absolute ethanol (Sigma Aldrich) solution and hydrochloric acid (HCl) 3wt% in aqueous (Merck) solution in equal (1:1) molar ratio. Methylamine was kept at 0 ⁰C and Hydrochloric acid was added drop wise to it and stirred for two hours. After that, rotary evaporator was used to get crystalline methylammoniumchloride (CH 3 NH 3 Cl). White colored precipitate confirmed the crystallization of CH 3 NH 3 Cl. Further, it was rinsed three times with diethyl ether for 30 min and dried using a rotary evaporator at 50⁰C followed by vacuum drying for over night. Methylammonium bromide (CH 3 NH 3 Br) precursor: We have used methylamine (CH 3 NH 2 ) 33 wt% in absolute ethanol (Sigma Aldrich) solution and hydrobromic acid (HBr) 4wt% in aqueous solution (Merck) at equal (1:1) molar ratio. Methylamine was poured into round bottom flask, kept at 0⁰C. Hydrobromic acid was added drop wise tomethylamine solution, and stirred it for two hours. After that, rotary evaporator was used to get crystalline methylammonium bromide (CH 3 NH 3 Br). Light orange color precipitate confirmed the crystallization of CH 3 NH 3 Br. Then it was rinsed three times with diethyl ether for 30 min and dried using rotary evaporator, at 50⁰C followed by vacuum drying overnight. Methylammonium Lead Bromide chlorideab(br 1-x Cl x ) 3 solution for blue LED: ABBr 3 solution was prepared using, Methylammonium Bromide precipitate and PbBr 2, are dissolved in DMSO (Dimethyl sulfoxide) in 1:1 molar ratio (ABBr 3 wt% perovskite in DMSO). Similarly for ABCl 3,Methylammoniumchloride precipitate and PbCl 2, dissolved in DMSO in 1:1 molar ratio (ABCl 3 wt% in DMSO). After that for AB(Br1-2

3 xcl) 3 solution, we mixed ABCl 3 and ABBr 3 in volumetric ratio (1:, 1:4, 3:,2:3, 1:1, :5, :3, 4:2, :1) in vials. The solution was stirred overnight at room temperature in nitrogen atmosphere. Light emitting diodes(leds) fabrication: ITO coated glass substrates (from Lumtec with sheet resistance ~ Ω/ ) were cleaned with soap water (Deconex), DI water, Acetone, and 2-propanol (IPA), for min successively in ultra sonicator. Oxygen plasma treatment was carried out at 0W for min on wet cleaned ITO substrates. A hole injection layer of poly(3,4- ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) (from Clevios) was spin coated at 4000 rpm for 0 seconds (thickness ~ 40 nm) on cleaned ITO substrate and annealed at 150⁰C for 30 min. in nitrogen atmosphere. After that the samples were transferred into nitrogen gas filled glove box. AB(Br 1-x Cl x ) 3 perovskite semiconductor layer was deposited on PEDOT:PSS layer by spin coating at 2000 rpm for 30 sec. Films were annealed at 0 ⁰C for 20 min. to evaporate the solvent and for better coverage. After this process, electron injection layer of PC 0 BM was deposited on perovskite film by spin coating at 2000 rpm for 30 sec (15 mg/ml in Chlorobenzene) and annealed at 50⁰C for 20 min. Top electrode of silver (200 nm) was deposited using thermal evaporation technique at 1x - mbar pressure at room temperature using 0.5 Å/s deposition rate. Devices were encapsulated in inert conditions. 3

4 Material Characterization XRD studies: The crystal structure analysis of perovskite films (AB(Br 1-x Cl x ) 3, were done by HRXRD (by RigakuSmartlab 3KW diffractometer) using Cu K α (λ =1.54 Å) on glass substrates. Morphology and halide composition studies: Perovskite films coverage on ITO/PEDOT:PSS substrates were studied using FESEM (ZEISS Field Emission Scanning Electron Microscopy ) as well composition analysis was done in EDX mode. Thicknesses of perovskite layers were measured by DektakXTprofilometer. Optical Studies: Absorbance and photoluminescence (PL) spectrum of perovskite films were measured on quartz substrate using UV-Vis-NIR Spectrometer (Perkin Elmer L50) and PL spectrometer (Cary Eclipse Spectrometer), respectively. We also carried out absolute PL yield measurement of these films using a calibrated large area photo-detector in vacuum condition by placing perovskite film (smaller than detector area) directly on top of detector in AC mode. It collects all forward emission photons, however, it losses light which is being scattered and wave-guided as substrate modes. Device Characterization: J-V-L characteristics were measured using, Multimeter (Keithley 2000), source meter (Keithley 2400) and a calibrated Si photo diode (from RS components). Electroluminescence spectra were collected using optical fiber connected UV-Vis-NIR spectrometer (using USB 4000 from Ocean optics). 4

5 ABBr 2.4 Cl 0.51 (a) ABBr1. Cl 1.14 (b) (c) ABBr 1.5 Cl 1.5 ABBr 1.0 Cl 1.2 (d) ABBr 0. Cl 2.13 (e) ABBr 0.21 Cl 2. (f) Figure S1 FESEM image of (a) ABBr 2.4 Cl 0.51 (b) ABBr 1. Cl 1.14 (c) ABBr 1.5 Cl 1.5 (d) ABBr 1.0 Cl 1.2 (e) ABBr 0. Cl 2.13 (f) ABBr 0.21 Cl 2. perovskite films on ITO/PEDOT:PSS substarte after annealing. We have observed perovskites film coverage is good and with chlorine content domain size of AB(Br 1-x Cl x ) 3 perovskite changed. 5

6 Table S1: Higher order X-ray diffraction peak position with different chlorine compositions Perovskite 2 nd order 2θ 3 rd order 2θ 4 th order 2θ peak (º) Peak (º) peak (º) ABBr ABBr 2.4 Cl ABBr 1. Cl ABBr 1. Cl ABBr 1.5 Cl ABBr 1.32 Cl ABBr 1.0 Cl ABBr 0.3 Cl ABBr 0. Cl ABBr 0.21 Cl ABCl

7 Normalized O.D ABBr 3 Excitonic Abs. Band to band Abs. (a) Normalized O.D ABCl 3 Excitonic Abs Band to band Abs. (b) Normalized O.D X=0.1 X=4 X=0. X=0.3 (c) Normalized PL x=0.3 x=0. x=4 x=0.1 (d) Wavelength (nm) Figure S2 (a) and (b) Deconvolution of excitonic absorption and band to band absorption for ABBr 3 and ABCl 3. (c) Optical density vs energy (normalized with respect to excitonic absorption peak for different chlorine compositions (x = 0.2, 0., 4 and 0.1) (d) Photoluminescence (PL) spectra (normalized) vs wavelength for different chlorine composition.

8 11 ABBr 3 ABBr 2.4 Cl 0.51 E u = 3 mev ln(α) cm -1 E u = 3 mev (a) ABBr 1. Cl 1.14 E u = 3 mev (c) energy (ev) (b) ABBr 1. Cl 1.32 E u = 3 mev (d) ABBr 1.5 Cl 1.5 E u = 45 mev ABBr 1.0 Cl 1.2 E u = 44 mev (e) ABBr 1.32 Cl 1. E u = 4 mev ABBr 0.3 Cl 2.0 E u = 44 mev (f) 5 (g) (h)

9 11 ABBr 0. Cl 2.13 ABBr 0.21 Cl 2. E u = 45 mev E u = 42 mev (i) (j) ABCl 3 E u = 43 mev (k) Figure S3. ln(α) (cm -1 ) vs energy (ev) spectrum of (a) ABBr 3 (b) ABBr 2.4 Cl 0.51 (c) ABBr 1. Cl 1.14 (d) ABBr 1. Cl 1.32 (e) ABBr 1.5 Cl 1.5 (f) ABBr 1.32 Cl 1. (g) ABBr 1.0 Cl 1.2 (h) ABBr 0.3 Cl 2.0 (i) ABBr 0. Cl 2.13 (j) ABBr 0.21 Cl 2. (k) ABCl 3 perovskite films on quartz substrate after annealing. Solid line is a linear fit to determine the slope at band-edge for these semiconductor films. Urbach energy (E u ) is calculated from the inverse of slope of ln(α) vs energy.

10 J(A/m 2 ) x (a) Voltage (V) L(cd/m 2 ) Current Eff.(cd/A) x (b) Voltage (V) EQE(%) x - 4 Figure S4 (a) Current density (J) (solid) & luminance (L) (open) vs applied bias (V) characteristics, (b) EQE (solid) & cd/a (open) vs voltage of blue emissive PeLED in ITO/PEDOT:PSS/ABBr 1.0 Cl 1.2 /Ag device structure. Luminance Eff. (cd/a) x -4 5 ABBr Cl 1.2 ABBr 1. Cl Luminance Eff (cd/a) x Voltage (V) Figure S5 Luminance Efficiency (cd/a) vs applied bias of blue and green emissive PeLED in ITO/PEDOT:PSS/ ABBr 1.0 Cl 1.2 (blue solid) or ABBr 1. Cl 1.14 (green solid)/pc 1 BM/Ag device structure calculated from J-V-L, respectively.