Code: FHI-aims

Level of theory: density functional theory

Exchange-correlation functional: PBE

Level of relativity: atomic ZORA

Basis set definition: tight

Numerical accuracy: tight

Comment: local structure optimization: unit cell + atomic positions [unconstrained] Files available on NOMAD: http://nomad-repository.eu:8080/NomadRepository-1.1/doi/result/index.zul?dataset=5842555

Code: FHI-aims

Level of theory: density functional theory

Exchange-correlation functional: PBE with Tkatchenko-Scheffler van der Waals correction

Level of relativity: atomic ZORA

Basis set definition: tight

Numerical accuracy: tight

Comment: local structure optimization: unit cell + atomic positions [unconstrained] Files available on NOMAD: http://nomad-repository.eu:8080/NomadRepository-1.1/doi/result/index.zul?dataset=5842555

Code: FHI-aims

Level of theory: density functional theory

Exchange-correlation functional: PBE with many-body dispersion (range-separated MBD@rsSCS)

Level of relativity: atomic ZORA

Basis set definition: tight

Numerical accuracy: tight

Comment: local structure optimization: unit cell + atomic positions [unconstrained] Files available on NOMAD: http://nomad-repository.eu:8080/NomadRepository-1.1/doi/result/index.zul?dataset=5842555

Starting materials: FTO (10 Ω/sq, Nippon Sheet Glass), TiCl4, HI, CH3NH2, PbI2

Product: MAPbI3 on TiO2-coated FTO, TiO2 film had a thickness of 8-12 μm. Powder is black.

Description: Soak FTO in a 40 mM TiCl4 aqueous solution at 70 °C for 30 min to form a thin TiO2 buffer layer. Coat FTO with a commercial nanocrystalline TiO2 paste (refer to SI for more information) using a screen printer and sintering at 480 °C for 1 h in air. Synthesize CH3NH3I by reacting HI with 40% methylamine in methanol solution followed by recrystallization. Drop the TiO2 film into an 8 wt % stoichiometric solution of CH3NH3I and PbI2 in γ-butyrolactone. Subsequent film formation was done by spin-coating.

Comment: The resultant mesoporous TiO2 (n-type semiconductor) film had a thickness of 8-12 μm. The liquid precursor film coated on the TiO2 gradually changed color simultaneously with drying, indicating the formation of CH3NH3PbI3 in the solid state. A vivid color change from yellowish to black is observed.

Method: Powder X-ray diffraction

Description: X-ray diffraction analysis (Rigaku RINT- 2500). Refer to Page 6050: Paragraph 2.

• Rayan C Duke University

Starting materials: HI, CH3NH2, Pb(NO3)2

Product: MAPbI3 Powder

Description: Add concentrated HI to neutralize 20 g of 40% CH3NH2 aqueous solution. Add 7.1 g (0.021 mol) of Pb(NO3)2 solution drop-wise under vigorous stirring at 100°C to the concentrated CH3NH2I solution. Organic crystals form while dripping in the solution. Cool the solution to not below 40°C and filter out the crystals. Wash crystals firstly with n-butanol and then with benzene; subsequently dry crystals in vacuum.

Comment: Synthesis references: [1] Canadian Journal of Chemistry, 1987, 65(5): 1042-1046 https://doi.org/10.1139/v87-176 [2] D. WEBER. Z. Naturforsch. 33b, 1443 (1978).

Method: X-ray diffraction

Description: Diffraction pattern of some of the lines corresponding to Weber's cubic (a = 6.27 A) were split up or broadened, indicating that MAPbI3 at room temperature is not strictly cubic. Refer to page 413 Experimental.

Starting materials: CH3NH3PbI3, lead (II) acetate, CH3NH3+ (by adding a 40% solution of CH3NH2 in water), concentrated HI

Product: Black and opaque MAPbI3 Single crystal

Description: CH3NH3PbI3 was synthesized from lead (II) acetate and CH3NH3+ (by adding a 40% solution of CH3NH2 in water) dissolved in concentrated HI solution. Cool aqueous solution from l00°C to not lower than 40°C to obtain a black crystal. Crystals of about 1 cm in dimension were obtained. Synthesis using reference [2].

Comment: Synthesis references: [1] K. Gesi: Ferroelectrics 203 (1997) 249. [2] A. Poglitsch and D. Weber, J. Chem. Phys., 1987, 87, 6373–6378. Atomic positions: Table II

Method: Single crystal X-ray diffraction

Description: Spherical samples were cut and polished into 0.3mm in diameter, among which a single crystal was selected and was mounted on an off-centered 4-circle diffractometer (HUBER 424) controlled by MXC (Mac Science). Graphite-monochromated Mo K\alpha radiation was used from a rotating anode generator with 50 kV–250 mA. Refer to Page 1695 Table I (Params); Page 1696 Table II (Apos).

• Rayan C Duke University

Starting materials: CH3NH3I [from syn], PbI2 [from syn], distilled HI (57% aqueous) (99.95%), H3PO2 (50% aqueous)

Product: Black MAPbI3 crystals

Description: Charge 100 ml 2-necked round bottom flask with a mixture of aqueous HI (6.8 ml, 7.58M) and aqueous H3PO2 (1.7 ml, 9.14M). The liquid was degassed by passing a stream of nitrogen through it for 1 min and keeping it under a nitrogen atmosphere throughout the experiment. Dissolve PbI2 (462 mg, 1 mmol) in the mixture upon heating the flask to 120 °C using an oil bath, under constant magnetic stirring, forming a bright yellow solution. Add solid CH3NH3I (159 mg, 1 mmol). Evaporate solution to approximately half its original volume by heating at 120 °C. Discontinue stirring and leave solution to cool back to room temperature. Upon cooling, black, rhombic dodecahedral crystals (12 faces) of the title compound precipitated. Leave crystals to grow for a further 24 h under a nitrogen atmosphere before filtering and washing copiously with degassed EtOH.

Method: Single crystal X-ray diffraction

Description: Single-crystal X-ray diffraction experiments were performed using either an STOE IPDS II or IPDS 2T diffractometer using Mo Kα radiation (λ = 0.71073 Å) and operating at 50 kV and 40 mA. Integration and numerical absorption corrections were performed using the X-AREA, X-RED, and X-SHAPE programs. Refer to Page 9025 Table 1.

• Rayan C Duke University

Starting materials: CH3NH3I [from syn], PbI2 [from syn], distilled HI 57% (99.95%), H3PO2 50%

Product: Black MAPbI3 crystals

Description: Charge 100 ml 2-necked round bottom flask with a mixture of aqueous HI (6.8 ml, 7.58M) and aqueous H3PO2 (1.7 ml, 9.14M). The liquid was degassed by passing a stream of nitrogen through it for 1 min and keeping it under a nitrogen atmosphere throughout the experiment. Dissolve PbI2 (462 mg, 1 mmol) in the mixture upon heating the flask to 120 °C using an oil bath, under constant magnetic stirring, forming a bright yellow solution. Add solid CH3NH3I (159 mg, 1 mmol). Evaporate solution to approximately half its original volume by heating at 120 °C. Discontinue stirring and leave solution to cool back to room temperature. Upon cooling, black, rhombic dodecahedral crystals (12 faces) of the title compound precipitated. Leave crystals to grow for a further 24 h under a nitrogen atmosphere before filtering and washing copiously with degassed EtOH. Yield 70-90%.

Method: Single crystal X-ray diffraction

Description: Single-crystal X-ray diffraction experiments were performed using either an STOE IPDS II or IPDS 2T diffractometer using Mo Kα radiation (λ = 0.71073 Å) and operating at 50 kV and 40 mA. Integration and numerical absorption corrections were performed using the X-AREA, X-RED, and X-SHAPE programs. Refer to Page 9025 Table 2.

• Rayan C Duke University

Starting materials: Lead(II) acetate (Chemical Reagents, Sigma), aqueous HI, CH3NH2 (40% soluble in water, Merck)

Product: Black MAPbI3 Polycrystals

Description: Following method by [1], dissolve 2.5 g of lead(II) acetate in 10 ml of concentrated (57% by weight) aqueous HI contained in a pyrex test tube and heat in a water bath. Add an additional 2 ml of HI solution with 0.597 g of CH3NH2 to the solution. Filter the black precipitate upon cooling from 100 °C to 46 °C over 6 hours and dry (100 °C/10 hours). Maintain solution temperature above 40 °C. Black crystals up to 2 mm long were obtained by cooling the solution over 4 days. Crystallization proceeded most rapidly at approximately 70 °C.

Comment: Synthesis references: [1] A. Poglitsch and D. Weber, J. Chem. Phys., 1987, 87, 6373–6378. [2] J. H. Im, C. R. Lee, J. W. Lee, S. W. Park and N. G. Park, Nanoscale, 2011, 3, 4088–4093.

Method: Powder X-ray diffraction

Description: Tetragonal/cubic phase transition was investigated using variable temperature powder X-ray diffraction. In situ XRD data were collected in asymmetric reflection mode under a static helium atmosphere on an INEL Equinox 3000 (Inel, Artenay, France) equipped with an XRK-900 reactor chamber (Anton-Paar, Graz, Austria), a curved position sensitive detector (Ine, Artenay, France), a copper Ka source and a Ge-(111) focusing mirror. Refer to Page 5636 Table 4.

• Rayan C Duke University

Starting materials: Methylamine (40% in methanol), hydroiodic acid (57 wt% in water), PbI2, g-butyrolactone, H2O2, NH4OH, Si wafer

Product: MAPbI3 film

Description: React 30 mL of methylamine and 32.3 mL of hydroiodic acid at 0 °C for 2 h. Evaporate solvents at 50 °C. Wash the yellowish raw CH3NH3I with diethyl ether by stirring the solution for 30min for a total of three times. Recrystallize CH3NH3I from a mixed solvent of diethyl ether and ethanol. Collect the solid and dry at 60 °C in a vacuum oven for 24 h. Treat Si wafer with an aqueous solution of H2O2 and NH4OH with a volume ratio of H2O2: NH4OH: H2O = 1: 1: 5 for 30 min. Drop a 40 wt% precursor solution of equimolar CH3NH3I and PbI2 in g-butyrolactone onto the Si wafer to form the MAPbI3 film. Spin-coat at 1500 rpm for 30 s, and then at 2500 rpm for 40 min in air. Upon drying at room temperature, color change indicates the formation of MAPbI3 in the solid state. Anneal the MAPbI3 film in air for 15 min at 100 °C.

Method: Powder X-ray diffraction

Description: The MAPbI3 film was characterized by X-ray diffraction (XRD) on a PANalytical X-ray diffractometer (Model EMPYREAN) with a monochromatic Cu Ka1 radiation. The lattice parameters were precisely determined using Si powders as the internal standard reference material. Refer to ESI Table SI.

• Rayan C Duke University

Starting materials: Methylamine (40% in methanol), hydroiodic acid (57 wt% in water), PbI2, g-butyrolactone, H2O2, NH4OH, Si wafer

Product: MAPbI3 film

Description: React 30 mL of methylamine and 32.3 mL of hydroiodic acid at 0 °C for 2 h. Evaporate solvents at 50 °C. Wash the yellowish raw CH3NH3I with diethyl ether by stirring the solution for 30min for a total of three times. Recrystallize CH3NH3I from a mixed solvent of diethyl ether and ethanol. Collect the solid and dry at 60 °C in a vacuum oven for 24 h. Treat Si wafer with an aqueous solution of H2O2 and NH4OH with a volume ratio of H2O2 : NH4OH : H2O = 1 : 1 : 5 for 30 min. Drop a 40 wt% precursor solution of equimolar CH3NH3I and PbI2 in g-butyrolactone onto the Si wafer to form the MAPbI3 film. Spin-coat at 1500 rpm for 30 s, and then at 2500 rpm for 40 min in air. Upon drying at room temperature, color change indicates the formation of MAPbI3 in the solid state. Anneal the MAPbI3 film in air for 15 min at 100 °C.

Method: Powder X-ray diffraction

Description: The MAPbI3 film was characterized by X-ray diffraction (XRD) on a PANalytical X-ray diffractometer (Model EMPYREAN) with a monochromatic Cu Ka1 radiation. The lattice parameters were precisely determined using Si powders as the internal standard reference material. Refer to ESI Table SI.

• Rayan C Duke University

Starting materials: Lead(II) acetate (Chemical Reagents, Sigma), aqueous HI, CH3NH2 (40% soluble in water, Merck)

Product: Black MAPbI3 polycrystals

Description: Following method by [1], dissolve 2.5 g of lead(II) acetate in 10 ml of concentrated (57% by weight) aqueous HI contained in a pyrex test tube and heat in a water bath. Add an additional 2 ml of HI solution with 0.597 g of CH3NH2 to the solution. Filter the black precipitate upon cooling from 100 °C to 46 °C over 6 hours and dry (100 °C/10 hours). Maintain solution temperature above 40 °C. Black crystals up to 2 mm long were obtained by cooling the solution over 4 days. Crystallization proceeded most rapidly at approximately 70 °C.

Comment: Synthesis references: [1] A. Poglitsch and D. Weber, J. Chem. Phys., 1987, 87, 6373–6378. [2] J. H. Im, C. R. Lee, J. W. Lee, S. W. Park and N. G. Park, Nanoscale, 2011, 3, 4088–4093.

Method: Powder X-ray diffraction

Description: Tetragonal/cubic phase transition was investigated using variable temperature powder X-ray diffraction. In situ XRD data were collected in asymmetric reflection mode under a static helium atmosphere on an INEL Equinox 3000 (Inel, Artenay, France) equipped with an XRK-900 reactor chamber (Anton-Paar, Graz, Austria), a curved position sensitive detector (Ine, Artenay, France), a copper Ka source and a Ge-(111) focusing mirror. Refer to Page 5636 Table 4.

Comment: Coexistent with tetragonal state

• Rayan C Duke University

Starting materials: HI (Sigma Aldrich), methylamine, PbI2 (99%, Sigma Aldrich), gamma-butyrolactone (Sigma Aldrich)

Product: Black MAPbI3 crystals

Description: MAPbI3 was synthesized using the method described by [2]. Make MAI by reacting a concentrated aqueous solution of hydroiodic acid with methylamine (40% in methanol) at 0 °C for 2 h with constant stirring. Evaporate at 50 °C in a rotary evaporator and wash the resulting precipitant three times with ethyl ether and dry in a vacuum at 60 °C for 24 h. Equimolar mixtures of the as-synthesised MAI and PbI2 in gamma-butyrolactone were left to stir overnight at 60 °C. The MAPbI3 product was obtained by drop-casting the as-prepared solutions on to glass substrates, which were then heated to 100 °C and annealed for 30 min. Crystalline MAPbI3 was recovered from the glass after cooling.

Comment: Synthesis references: [1] A. Poglitsch and D. Weber, J. Chem. Phys., 1987, 87, 6373–6378. [2] J. H. Im, C. R. Lee, J. W. Lee, S. W. Park and N. G. Park, Nanoscale, 2011, 3, 4088–4093.

Method: Single crystal X-ray diffraction

Description: A small fragment (approximately 0.1 mm X 0.1 mm X 0.1 mm) was cleaved from one of the solution-grown single crystals. Data were collected on a Bruker Smart Apex II three-circle diffractometer at various temperatures between room temperature and 100 K using Mo Ka radiation with a graphite monochromator over the angular range 2.5 to 30.5° 2theta. Refer to Page 5637 Table 8.

Starting materials: HI (Sigma Aldrich), methylamine, PbI2 (99%, Sigma Aldrich), gamma-butyrolactone (Sigma Aldrich)

Product: Black MAPbI3 crystals

Description: MAPbI3 was synthesized using the method described by [2]. Make MAI by reacting a concentrated aqueous solution of hydroiodic acid with methylamine (40% in methanol) at 0 °C for 2 h with constant stirring. Evaporate at 50 °C in a rotary evaporator and wash the resulting precipitant three times with ethyl ether and dry in a vacuum at 60 °C for 24 h. Equimolar mixtures of the as-synthesised MAI and PbI2 in gamma-butyrolactone were left to stir overnight at 60 °C. The MAPbI3 product was obtained by drop-casting the as-prepared solutions on to glass substrates, which were then heated to 100 °C and annealed for 30 min. Crystalline MAPbI3 was recovered from the glass after cooling.

Comment: Synthesis references: [1] A. Poglitsch and D. Weber, J. Chem. Phys., 1987, 87, 6373–6378. [2] J. H. Im, C. R. Lee, J. W. Lee, S. W. Park and N. G. Park, Nanoscale, 2011, 3, 4088–4093.

Method: Single crystal X-ray diffraction

Description: A small fragment (approximately 0.1 mm X 0.1 mm X 0.1 mm) was cleaved from one of the solution grown single crystals. Data were collected on a Bruker Smart Apex II three-circle diffractometer at various temperatures between room temperature and 100 K using Mo Ka radiation with a graphite monochromator over the angular range 2.5 to 30.5° 2theta. Refer to Page 5637 Table 8.

• Rayan C Duke University

Starting materials: Lead acetate, HI (aq., 57 wt%), CH3NH2 (aq., 40%)

Product: Yellow MAPbI3 thin film (10 nm grain size)

Description: Dissolve 2.5 g of lead acetate (Sigma) in 10 mL hydroiodic acid (aq., 57 wt%, Sigma) in a 50 mL round bottom flask and heat to 100 °C in an oil bath. Add 0.597 g of CH3NH2 (aq., 40%, Sigma) dropwise to a further 2 mL of hydroiodic acid kept at 0 °C in an ice bath under stirring. Add the methylammonium iodide solution to the lead acetate solution and cool over two hours to 46 °C, affording a black precipitate. Filter and dry the black precipitate for 12 h at 100 °C. Average yield was 3.1 g, 75.2%. Repeat until 8 g of product has been obtained.

Comment: MAPbI3 was prepared according to the method of A. Poglitsch and D. Weber, J. Chem. Phys., 1987, 87, 6373–6378. CIF file: Fachinformationszentrum Karlsruhe, 76344 Eggenstein-Leopoldshafen (Germany), CSD 428898

Method: Powder neutron diffraction

Description: Data were collected using the D20 instrument at the ILL Grenoble operating in high take-off angle, higher resolution mode. 8 g of finely ground MAPbI3 was placed in a 7 mm diameter vanadium can. Data were collected for 90 minutes at 100 K. Raw diffraction data were corrected against detector efficiency and analysed using the GSAS/EXPGUI program suite; structure refinements for the long data collections at 100, 180 and 350 K were undertaken as described in the ESI. Refer to a,b,c, space group from ESI Table S1.1, volume from Garnett PRL, Structure Refinement from ESI.

• Rayan C Duke University

Starting materials: Lead acetate, HI (aq., 57 wt%), CH3NH2 (aq., 40%)

Product: Yellow MAPbI3 thin film (10 nm grain size)

Description: Dissolve 2.5 g of lead acetate (Sigma) in 10 mL hydroiodic acid (aq., 57 wt%, Sigma) in a 50 mL round bottom flask and heat to 100 °C in an oil bath. Add 0.597 g of CH3NH2 (aq., 40%, Sigma) dropwise to a further 2 mL of hydroiodic acid kept at 0 °C in an ice bath under stirring. Add the methylammonium iodide solution to the lead acetate solution and cool over two hours to 46 °C, affording a black precipitate. Filter and dry the black precipitate for 12 h at 100 °C. Average yield was 3.1 g, 75.2%. Repeat until 8 g of product has been obtained.

Comment: MAPbI3 was prepared according to the method of A. Poglitsch and D. Weber, J. Chem. Phys., 1987, 87, 6373–6378. CIF file: Fachinformationszentrum Karlsruhe, 76344 Eggenstein-Leopoldshafen (Germany), CSD 428900

Method: Powder neutron diffraction

Description: Data were collected using the D20 instrument at the ILL Grenoble operating in high take-off angle, higher resolution mode. 8 g of finely ground MAPbI3 was placed in a 7 mm diameter vanadium can. Data were collected for 90 minutes at 352 K. Raw diffraction data were corrected against detector efficiency and analysed using the GSAS/EXPGUI program suite; structure refinements for the long data collections at 100, 180 and 350 K were undertaken as described in the ESI. Refer to ESI Table S3.1.

• Rayan C Duke University

Code: VASP

Level of theory: DFT

Exchange-correlation functional: PBE-GGA

K-point grid: 7x5x7

Level of relativity: Non-relativistic

Basis set definition: Plane-wave with cutoff 900 eV

Numerical accuracy: Tolerance for energy minimization 10e-9 eV/atom. interatomic forces after relaxation were below 0.005 eV/Å, and the stresses were below 0.05 GPa

Comment: Local structure optimization: Unit cell + atomic positions [with symmetry constraints], Geometry input source: From Expt ID 19

• Rayan C Duke University

Code: VASP

Level of theory: DFT

Exchange-correlation functional: PBE-GGA

K-point grid: 2x5x7

Level of relativity: Non-relativistic

Basis set definition: Plane-wave with cutoff 900 eV

Numerical accuracy: Tolerance: 10e-9 eV

Comment: Local structure optimization: Unit cell + atomic positions [with symmetry constraints], Geometry input source: From Expt ID 19

Starting materials: CD3ND2DCl (Sigma-Aldrich, 98 atom % D), DI, D2O, PbI2 (Acros Organics)

Product: Black d6-MAPbI3 powder

Description: Dissolve 1.0 g of CD3ND2DCl in 15 g of 16% DI in D2O (made by dissolving 5 g DI gas in 25 g D2O) and pump to dryness to yield CD3ND2DI. Add material to 6 g of lead iodide and mix in ~25mL of DMF. Upon stirring, obtain pale yellow clear solution. Warm resulting solution and stir overnight in a N2 glove box. Evaporate solution to dryness under vacuum and wash the resulting black solution with dichloromethane and n-propanol. Isolate using suction drying. Anneal solid in nitrogen in the glove box at 140 °C for 1hr to remove residual solvent. Expect to yield 7.95 g of d6-MAPbI3 (97% yield).

Comment: Deuterated sample MAPbI3 (d6-CD3ND3PbI3)

Method: Neutron diffraction

Description: Samples were loaded into 8mm diameter vanadium cans in a helium glove- box for analysis on the POWGEN diffractometer situated at the Spallation Neutron Source, Oak Ridge National Laboratory. The sample size was ~5.5 g for the d6-MAPbI. The analyses of the POWGEN data were carried out using the TOPAS refinement package for Rietveld. Refer to SI: Supplementary Table 1 and Additional dataset; CCDC.

Comment: Deuterated sample MAPbI3 (d6-CD3ND3PbI3)

• Rayan C Duke University

Starting materials: CD3ND2DCl (Sigma-Aldrich, 98 atom % D), DI, D2O, PbI2 (Acros Organics)

Product: Black d6-MAPbI3 powder

Description: Dissolve 1.0 g of CD3ND2DCl in 15 g of 16% DI in D2O (made by dissolving 5 g DI gas in 25 g D2O) and pump to dryness to yield CD3ND2DI. Add material to 6 g of lead iodide and mix in ~25mL of DMF. Upon stirring, obtain pale yellow clear solution. Warm resulting solution and stir overnight in a N2 glove box. Evaporate solution to dryness under vacuum and wash the resulting black solution with dichloromethane and n-propanol. Isolate using suction drying. Anneal solid in nitrogen in the glove box at 140 °C for 1hr to remove residual solvent. Expect to yield 7.95 g of d6-MAPbI3 (97% yield).

Comment: Deuterated sample: MAPbI3 (d6-CD3ND3PbI3)

Method: Neutron diffraction

Description: Samples were loaded into 8mm diameter vanadium cans in a helium glove- box for analysis on the POWGEN diffractometer situated at the Spallation Neutron Source, Oak Ridge National Laboratory. The sample size was ~5.5 g for the d6-MAPbI. The analyses of the POWGEN data were carried out using the TOPAS refinement package for Rietveld. Refer to SI: Supplementary Table 4 and Additional dataset; CCDC.

Comment: Deuterated sample: MAPbI3 (d6-CD3ND3PbI3)

• Rayan C Duke University

Starting materials: CD3ND2DCl (Sigma-Aldrich, 98 atom % D), DI, D2O, PbI2 (Acros Organics)

Product: Black d6-MAPbI3 powder

Description: Dissolve 1.0 g of CD3ND2DCl in 15 g of 16% DI in D2O (made by dissolving 5 g DI gas in 25 g D2O) and pump to dryness to yield CD3ND2DI. Add material to 6 g of lead iodide and mix in ~25mL of DMF. Upon stirring, obtain pale yellow clear solution. Warm resulting solution and stir overnight in a N2 glove box. Evaporate solution to dryness under vacuum and wash the resulting black solution with dichloromethane and n-propanol. Isolate using suction drying. Anneal solid in nitrogen in the glove box at 140 °C for 1hr to remove residual solvent. Expect to yield 7.95 g of d6-MAPbI3 (97% yield).

Comment: Deuterated sample: MAPbI3 (d6-CD3ND3PbI3)

Method: Neutron diffraction

Description: Samples were loaded into 8mm diameter vanadium cans in a helium glove- box for analysis on the POWGEN diffractometer situated at the Spallation Neutron Source, Oak Ridge National Laboratory. The sample size was ~5.5 g for the d6-MAPbI. The analyses of the POWGEN data were carried out using the TOPAS refinement package for Rietveld. Refer to SI: Supplementary Table 5.

Comment: Deuterated sample: MAPbI3 (d6-CD3ND3PbI3)

• Rayan C Duke University

Starting materials: CD3NH2 (Sigma-Aldrich, 99 atom % D)

Product: CD3NH3PbI3

Description: The CD3NH3PbI3 was prepared using CD3NH2 that was 99 atom % D. Synthesis perovskite using a similar method as 4-a.

Comment: Partially deuterated sample: MAPbI3 (d3-CD3NH3PbI3)

Method: Neutron diffraction

Description: Samples were loaded into 8mm diameter vanadium cans in a helium glove- box for analysis on the POWGEN diffractometer situated at the Spallation Neutron Source, Oak Ridge National Laboratory. The analyses of the POWGEN data were carried out using the TOPAS refinement package for Rietveld. Refer to Additional dataset; CCDC.

Comment: Partially deuterated sample: MAPbI3 (d3-CD3NH3PbI3)

• Rayan C Duke University

Starting materials: CH3NH2, HI, D2O

Product: CH3ND3PbI3

Description: Preparation of CH3ND3I: React methylamine gas with HI to yield methyl ammonium iodide. Exchange the two H atoms attached to the nitrogen atoms with D by dissolving the salt in 10 ml D2O (99 atom % D), drying under vacuum, and then repeating two more times. The resulting CH3ND3I was estimated to be better than 98 atom% D on the ammonium group. Synthesis perovskite using a similar method as 4-a.

Comment: Partially deuterated: MAPbI3 (d3-CH3ND3PbI3)

Method: Neutron diffraction

Description: Samples were loaded into 8mm diameter vanadium cans in a helium glove- box for analysis on the POWGEN diffractometer situated at the Spallation Neutron Source, Oak Ridge National Laboratory. The analyses of the POWGEN data were carried out using the TOPAS refinement package for Rietveld. Refer to Additional dataset; CCDC.

Comment: Partially deuterated: MAPbI3 (d3-CH3ND3PbI3)

• Rayan C Duke University

Starting materials: HI (Sigma Aldrich), methylamine, PbI2 (99%, Sigma Aldrich), gamma-butyrolactone (Sigma Aldrich)

Product: Black MAPbI3 crystals

Description: MAPbI3 was synthesized using the method described by [2]. Make MAI by reacting a concentrated aqueous solution of hydroiodic acid with methylamine (40% in methanol) at 0 °C for 2 h with constant stirring. Evaporate at 50 °C in a rotary evaporator and wash the resulting precipitant three times with ethyl ether and dry in a vacuum at 60 °C for 24 h. Equimolar mixtures of the as-synthesised MAI and PbI2 in gamma-butyrolactone were left to stir overnight at 60 °C. The MAPbI3 product was obtained by drop-casting the as-prepared solutions on to glass substrates, which were then heated to 100 °C and annealed for 30 min. Crystalline MAPbI3 was recovered from the glass after cooling.

Comment: Synthesis references: [1] A. Poglitsch and D. Weber, J. Chem. Phys., 1987, 87, 6373–6378. [2] J. H. Im, C. R. Lee, J. W. Lee, S. W. Park and N. G. Park, Nanoscale, 2011, 3, 4088–4093. Atomic coordinates in Table 7.

Method: Single crystal X-ray diffraction

Description: A small fragment (approximately 0.1 mm X 0.1 mm X 0.1 mm) was cleaved from one of the solution grown single crystals. Data were collected on a Bruker Smart Apex II three-circle diffractometer at various temperatures between room temperature and 100 K using Mo Ka radiation with a graphite monochromator over the angular range 2.5 to 30.5° 2theta. Refined. Refer to Page 5636 Table 6, 7.

Comment: Table 7 for atomic positions

• Rayan C Duke University

Starting materials: Lead(II) acetate (Chemical Reagents, Sigma), concentrated aqueous HI, CH3NH2 (40% soluble in water, Merck)

Product: Black MAPbI3 crystals

Description: Precipitate polycrystalline MAPbI3 from a halogenated acid solution using the method of [1]. Dissolve 1.88 g of lead(II) acetate in 40 ml concentrated to 57 wt% HI aqueous solution warmed (~90 °C) in a water bath. Then add another 2 ml of HI solution with 0.45 g CH3NH2. Crystallize by cooling the solution from 90 °C to room temperature over 3 hours. Wash product with acetone and dry overnight at 100 °C in a vacuum oven. Obtain larger crystals via slow cooling from 90 to 50 °C over 3 days.

Comment: Synthesis references: [1] A. Poglitsch and D. Weber, J. Chem. Phys., 1987, 87, 6373–6378. [2] Q. Xu, T. Eguchi, H. Nakayama, N. Nakamura and M. Kishita, Z. Naturforsch., A: Phys. Sci., 1991, 46, 240–246.

Method: Single crystal X-ray diffraction

Description: Agilent Supernova diffractometer (Mo Kα, λ = 0.71073 Å) fitted with an Atlas detector, using Mo radiation. Allow crystal of MAPbI3 to equilibrate for at least one hour after the phase transition to obtain a higher quality dataset. Automated data processing and indexing procedures contained within the CrysAlisPro software. Refer to Page 9304 Section 3.4 Paragraph 2.

• Rayan C Duke University

Starting materials: Lead acetate, HI (aq., 57 wt%), CH3NH2 (aq., 40%)

Product: Yellow MAPbI3 thin film (10 nm grain size)

Description: Dissolve 2.5 g of lead acetate (Sigma) in 10 mL hydroiodic acid (aq., 57 wt%, Sigma) in a 50 mL round bottom flask and heat to 100 °C in an oil bath. Add 0.597 g of CH3NH2 (aq., 40%, Sigma) dropwise to a further 2 mL of hydroiodic acid kept at 0 °C in an ice bath under stirring. Add the methylammonium iodide solution to the lead acetate solution and cool over two hours to 46 °C, affording a black precipitate. Filter and dry the black precipitate for 12 h at 100 °C. Average yield was 3.1 g, 75.2%. Repeat until 8 g of product has been obtained.

Comment: MAPbI3 was prepared according to the method of A. Poglitsch and D. Weber, J. Chem. Phys., 1987, 87, 6373–6378. CIF file is available at Fachinformationszentrum Karlsruhe, 76344 Eggenstein-Leopoldshafen (Germany), CSD 428899.

Method: Powder neutron diffraction

Description: Data were collected using the D20 instrument at the ILL Grenoble operating in high take-off angle, higher resolution mode. 8 g of finely ground MAPbI3 was placed in a 7 mm diameter vanadium can. Data were collected for 90 minutes at 180 K. Raw diffraction data were corrected against detector efficiency and analysed using the GSAS/EXPGUI program suite; structure refinements for the long data collections at 100, 180 and 350 K were undertaken as described in the ESI. Refer to ESI Table S2.1.

• Rayan C Duke University

Starting materials: lead (II) acetate, CH3NH3+ (by adding a 40% solution of CH3NH2 in water), concentrated HI

Product: Black MAPbI3 crystals

Description: CH3NH3PbI3 was synthesized from lead (II) acetate and CH3NH3+ dissolved in a concentrated HI solution. The aqueous solution was cooled from l00°C to 40°C to obtain the black crystals.

Method: temperature-dependent Guinier-Simon photograph

Description: No experimental details reported. Refer to Page 6374 Table I.

• Rayan C Duke University

Starting materials: lead (II) acetate, CH3NH3+ (by adding a 40% solution of CH3NH2 in water), concentrated HI

Product: Black MAPbI3 crystals

Description: CH3NH3PbI3 was synthesized from lead (II) acetate and CH3NH3+ dissolved in a concentrated HI solution. The aqueous solution was cooled from l00°C to 40°C to obtain the black crystals.

Method: temperature-dependent Guinier-Simon photograph

Description: No experimental details reported. Refer to Page 6374 Table I.

• Rayan C Duke University

Starting materials: lead (II) acetate, CH3NH3+ (by adding a 40% solution of CH3NH2 in water), concentrated HI

Product: Black MAPbI3 crystals

Description: CH3NH3PbI3 was synthesized from lead (II) acetate and CH3NH3+ dissolved in a concentrated HI solution. The aqueous solution was cooled from l00°C to 40°C to obtain the black crystals.

Method: temperature-dependent Guinier-Simon photograph

Description: No experimental details reported. Refer to Page 6374 Table I.

• Rayan C Duke University

Starting materials: Lead(II) acetate (Chemical Reagents, Sigma), concentrated aqueous HI, CH3NH2 (40% soluble in water, Merck)

Product: Black MAPbI3 Single crystal

Description: Precipitate polycrystalline MAPbI3 from a halogenated acid solution using the method of [1]. Dissolve 1.88 g of lead(II) acetate in 40 ml concentrated to 57 wt% HI aqueous solution warmed (~90 °C) in a water bath. Then add another 2 ml of HI solution with 0.45 g CH3NH2. Crystallize by cooling the solution from 90 °C to room temperature over 3 hours. Wash product with acetone and dry overnight at 100 °C in a vacuum oven. Obtain larger crystals via slow cooling from 90 to 50 °C over 3 days.

Comment: Synthesis references: [1] A. Poglitsch and D. Weber, J. Chem. Phys., 1987, 87, 6373–6378. [2] Q. Xu, T. Eguchi, H. Nakayama, N. Nakamura and M. Kishita, Z. Naturforsch., A: Phys. Sci., 1991, 46, 240–246. Atomic positions: Table S4.

Method: X-ray diffraction

Description: Agilent Supernova diffractometer (Mo Kα, λ = 0.71073 Å) fitted with an Atlas detector, using Mo radiation. Allow crystal of MAPbI3 to equilibriate for at least one hour after the phase transition to obtain a higher quality dataset. Manual indexing routine. Refer to Page 9304 Section 3.4 Paragraph 2; SI Table S3.

Comment: P4mm space group. Two distinct cells possible, this and the hexagonal one. Choose hexagonal.

• Rayan C Duke University

Starting materials: Lead(II) acetate (Chemical Reagents, Sigma), concentrated aqueous HI, CH3NH2 (40% soluble in water, Merck)

Product: Black MAPbI3 Single crystal

Description: Precipitate polycrystalline MAPbI3 from a halogenated acid solution using the method of [1]. Dissolve 1.88 g of lead(II) acetate in 40 ml concentrated to 57 wt% HI aqueous solution warmed (~90 °C) in a water bath. Then add another 2 ml of HI solution with 0.45 g CH3NH2. Crystallize by cooling the solution from 90 °C to room temperature over 3 hours. Wash product with acetone and dry overnight at 100 °C in a vacuum oven. Obtain larger crystals via slow cooling from 90 to 50 °C over 3 days.

Comment: Synthesis references: [1] A. Poglitsch and D. Weber, J. Chem. Phys., 1987, 87, 6373–6378. [2] Q. Xu, T. Eguchi, H. Nakayama, N. Nakamura and M. Kishita, Z. Naturforsch., A: Phys. Sci., 1991, 46, 240–246. Atomic positions: Table S4. Atomic positions: Table S6 (R-3m) & Table S7 (R3m)

Method: X-ray diffraction

Description: Agilent Supernova diffractometer (Mo Kα, λ = 0.71073 Å) fitted with an Atlas detector, using Mo radiation. Allow crystal of MAPbI3 to equilibrate for at least one hour after the phase transition to obtain a higher quality dataset. Manual indexing routine. Refer to Page 9304 Section 3.4 Paragraph 2; SI Table S5.

Comment: Two distinct cells are possible - this and the tetragonal one. Choose this because of its higher symmetry. The equivalent rhombohedral structure has cell constants: a = 6.3222(4) Å; α = β = γ = 90.021(4)°.

• Rayan C Duke University

Starting materials: Lead(II) acetate (Chemical Reagents, Sigma), concentrated aqueous HI, CH3NH2 (40% soluble in water, Merck)

Product: Black MAPbI3 Single crystal

Description: Precipitate polycrystalline MAPbI3 from a halogenated acid solution using the method of [1]. Dissolve 1.88 g of lead(II) acetate in 40 ml concentrated to 57 wt% HI aqueous solution warmed (~90 °C) in a water bath. Then add another 2 ml of HI solution with 0.45 g CH3NH2. Crystallize by cooling the solution from 90 °C to room temperature over 3 hours. Wash product with acetone and dry overnight at 100 °C in a vacuum oven. Obtain larger crystals via slow cooling from 90 to 50 °C over 3 days.

Comment: Synthesis references: [1] A. Poglitsch and D. Weber, J. Chem. Phys., 1987, 87, 6373–6378. [2] Q. Xu, T. Eguchi, H. Nakayama, N. Nakamura and M. Kishita, Z. Naturforsch., A: Phys. Sci., 1991, 46, 240–246.

Method: X-ray diffraction

Description: Agilent Supernova diffractometer (Mo Kα, λ = 0.71073 Å) fitted with an Atlas detector, using Mo radiation. Allow crystal of MAPbI3 to equilibrate for at least one hour after the phase transition to obtain a higher quality dataset. Manual indexing routine. Refer to Page 9304 Section 3.4 Paragraph 2; SI Table S5.

Comment: Equivalent to the hexagonal structure

• Rayan C Duke University

Code: FHI-aims

Level of theory: density functional theory

Exchange-correlation functional: PBE with Tkatchenko-Scheffler van der Waals correction

K-point grid: 1x2x2

Level of relativity: atomic ZORA

Basis set definition: tight

Numerical accuracy: tight

Comment: local structure optimization: unit cell + atomic positions [unconstrained]Files available on NOMAD: http://nomad-repository.eu:8080/NomadRepository-1.1/doi/result/index.zul?dataset=5842555

Method: Single-Crystal X-ray Diffraction

Description: Frames were collected using a Bruker D85 diffractometer equipped with a Photon 100 CMOS detector. Synchrotron X-rays at Beamline 11.3.1 at the ALS, LBNL were monochromated using silicon(111).

• Rayan C Duke University

Starting materials: Presumably (by analogy with MAPbBr3 synthesis description in same reference): 40% aqueous CH3NH2 solution; concentrated HI(aq); Pb(NO3)2 (aq; 0.021 molar)

Product: black crystals

Description: Adapted from synthesis description of CH3NH3PbBr3 as indicated by the author. Neutralize 20g of 40% aq. CH3NH2 solution with concentrated aq. HI. At 100 deg. C, add aq. (0.021 mol) solution of Pb(NO3)2 by slow dripping while stirring vigorously. Crystals begin to form while stirring. During synthesis of CH3NH3PbI3, it is important to keep the temperature of the solution above 40 degrees Celsius at all times. Solution is filtrated after cooling to room temperature. The crystals are washed with n-butanol and subsequently benzene and are finally dried in vacuum. Nominal stoichiometry: C 1.94 wt.% H 0.98 wt.% N 2.26 wt.% Pb(II) 33.42 wt.% I 61.41 wt.% Actual stoichiometry: C 1.92 wt.% H 1.01 wt.% N 2.29 wt.% Pb(II) 33.4 wt.% I 61.3 wt.%

Method: Powder X-ray diffraction (PXRD)

Description: X-ray powder diagrams collected with a Debye-Scherrer camera using Cu K-alpha radiation (wave length 1.54178 Angstrom).

Comment: Miss Leonhardt recorded the PXRD diagrams.

• Volker Blum Duke University