Crystal system: tetragonal
| Band gap (optical, diffuse reflectance), eV |
|---|
Starting materials: Lead(II) acetate (Chemical Reagents, Sigma), concentrated aqueous HI, CH3NH2 (40% soluble in water, Merck)
Product: 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. Refer to Page 9299 Section 2.1 Synthesis.
Comment: Black crystals; 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: UV-Vis absorption (diffuse reflectance)
Description: UV-Visible-NIR spectrophotometer (Shimadzu UV-3600) with integrating sphere attachment (ISR-3100) operating in the 300–1500 nm region. Highly refined barium sulfate powder (Wako, pure) was used as a reflectance standard. Optical absorption coefficient was determined according to the Kubelka–Munk equation. In this manner, optical band gaps for the perovskites were determined. Refer to Page 9300 Section 3.1 Paragraph 3; Figure 3,4.
Crystal system: unknown
| Band gap (optical, diffuse reflectance), eV |
|---|
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 the 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: Optical-diffuse reflectance
Description: Measurements were performed at room temperature using a Shimadzu UV-3101 PC double-beam, double-monochromator spectrophotometer operating from 200 to 2500 nm. BaSO4 was used as a nonabsorbing reflectance reference. The generated reflectance-versus-wavelength data were used to estimate the band gap of the material by converting reflectance to absorbance data according to the Kubelka−Munk equation: α/S =(1 − R)^2/2R, where R is the reflectance and α and S are the absorption and scattering coefficients, respectively. Refer to Page 9029 Figure 9.
Crystal system: tetragonal
| Band gap (optical, diffuse reflectance), eV |
|---|
Starting materials: CH3NH3I, PbI2
Product: Black MAPbI3 Solid
Description: Load equimolar amounts of PbI2 and MAI in a 9mm pyrex tube. Shake materials mechanically to ensure a homogenous mixture. Place the tube on a sealing line evacuated to 10-4 mbar and flame sealed. Immerse tube on a sand bath standing at 200 °C, such that the mixture of solids was heated homogeneously. Maintain 4/5 of the tube outside the bath at room temperature. Leave solids in the bath for 2 h to form a homogeneous black solid.
Method: Optical-diffuse reflectance
Description: Measurements were performed at room temperature using a Shimadzu UV-3101 PC double-beam, double-monochromator spectrophotometer operating from 200 to 2500 nm. BaSO4 was used as a nonabsorbing reflectance reference. The generated reflectance-versus-wavelength data were used to estimate the band gap of the material by converting reflectance to absorbance data according to the Kubelka−Munk equation: α/S =(1 − R)^2/2R, where R is the reflectance and α and S are the absorption and scattering coefficients, respectively. Refer to Page 9029 Figure 9.
Crystal system: unknown
| Band gap (optical, diffuse reflectance), eV |
|---|
Starting materials: CH3NH3I, PbI2
Product: Black MAPbI3 Ingot
Description: Load equimolar amounts of PbI2 and MAI in a 15mm pyrex test tube. Shake materials mechanically to ensure a homogenous mixture. Immerse in a sand bath standing at 350 °C under a gentle flow of nitrogen. The reaction proceeds within 0.5-1 min. Pb-containing solids decompose on prolonged heating (> 3 min) or by raising the temperature above 400 °C, through evolution of I2 gas, crystallizing on the cooler walls of the tube.
Method: Optical-diffuse reflectance
Description: Measurements were performed at room temperature using a Shimadzu UV-3101 PC double-beam, double-monochromator spectrophotometer operating from 200 to 2500 nm. BaSO4 was used as a nonabsorbing reflectance reference. The generated reflectance-versus-wavelength data were used to estimate the band gap of the material by converting reflectance to absorbance data according to the Kubelka−Munk equation: α/S =(1 − R)^2/2R, where R is the reflectance and α and S are the absorption and scattering coefficients, respectively. Refer to Page 9029 Figure 9.
Crystal system: unknown
| Band gap (optical, diffuse reflectance), eV |
|---|
Starting materials: CH3NH3I, PbI2
Product: Black MAPbI3 Powder
Description: Place equimolar amounts of PbI2 and MAI in an agate mortar and ground carefully with a pestle until a visually homogeneous, black powder is obtained.
Method: Optical diffuse reflectance
Description: Measurements were performed at room temperature using a Shimadzu UV-3101 PC double-beam, double-monochromator spectrophotometer operating from 200 to 2500 nm. BaSO4 was used as a nonabsorbing reflectance reference. The generated reflectance-versus-wavelength data were used to estimate the band gap of the material by converting reflectance to absorbance data according to the Kubelka−Munk equation: α/S =(1 − R)^2/2R, where R is the reflectance and α and S are the absorption and scattering coefficients, respectively. Refer to Page 9029 Figure 9.
Crystal system: tetragonal
| Band gap (optical, diffuse reflectance), eV |
|---|
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.