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: Diffuse-reflectance UV-Vis absorption

Description: Absorption optical gap is 1.51 eV using diffuse reflectance UV-Vis spectra calculated using the optical absorption coefficient (\alpha) according to the Kubelka-Munk equation. Refer to Page 5637 Figure 11.

• 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: 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: 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

Code: CASTEP 50

Level of theory: DFT

Exchange-correlation functional: PBE-GGA

K-point grid: 4x4x4

Comment: CH3NH3+ was ignored. Refer to Page 5638; Page 5639 Figure 15 (a).

• Ruyi Song Chemistry department, Duke university

Code: CASTEP 50

Level of theory: DFT

Exchange-correlation functional: PBE-GGA

K-point grid: 4x4x4

Comment: CH3NH3+ was ignored. Refer to Page 5638; Page 5639 Figure 15 (b).

• Ruyi Song Chemistry department, Duke university

Code: CASTEP 50

Level of theory: DFT

Exchange-correlation functional: PBE-GGA

K-point grid: 4x4x4

Comment: CH3NH3+ was ignored. Refer to Page 5638; Page 5639 Figure 17 (b).

• Ruyi Song Chemistry department, Duke university

Code: CASTEP 50

Level of theory: DFT

Exchange-correlation functional: PBE-GGA

K-point grid: 4x4x4

Comment: CH3NH3+ included, SC-XRD of Synthesis ID-34. Refer to Page 5638; Page 5639 Figure 15 (c), Figure 17 (a).

• Ruyi Song Chemistry department, 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) focussing mirror. Two different heating experiments were conducted. In the first, MAPbI3 was heated to 85 °C in five degree steps starting from 25 °C, with data collected for 5 minutes at each holding temperature. The second experiment employed a continuous heating ramp at a rate of 1° min^-1 during which 30 measurements of 120 seconds were performed. Each measurement corresponds to a temperature span of 2 °C; the final temperature of each measurement was recorded in the measurement file. Five empty sample holder measurements were conducted at room temperature in order to establish the chamber background. Refer to Page 5633 Results and discussion; Page 5634 Figure 4 and Figure 5.

Comment: Transition approximately from (327 - 330 K, 54 - 57 °C), large change in diffraction intensity at 57 °C weak scattering persists up to 75 °C on heating collected at 2 °C intervals.

• Rayan C Duke University

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

Product: Black MAPbI3 Single 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 ° 2\theta. Refer to Page 5637 Figure 11.

Comment: Author did not formally state 152 K as the transition temperature. But lattice parameters provided in Table 8 supports this conclusion.

• Rayan C Duke University