Starting materials: FAI, PbI2, N,N-dimethylformamide (DMF)
Product: FAPbI3 film
Description: FAI and PbI2 were dissolved in anhydrous DMF in a 1:1 molar ratio, at 0.88M. 60µl of hydroiodic acid (57%w/w) was added to 1ml of the solution. The FAPbI3 precursor was diluted down to 0.55M with DMF. The precursor solution was spin-coated and annealed on glass in a nitrogen-filled glovebox at 170°C for 25 minutes.
Method: optical absorption
Description: Transmittance and reflectance spectra were collected with a Varian Cary 300 UV-Vis spectrophotometer with an internally coupled integrating sphere.
Starting materials: formamidine acetate salt, hydroiodic acid, lead iodide
Product: thin film
Description: By reaction of 20 of formamidine acetate salt with 30 mL of hydroiodic acid (57 wt% in H20) at 60°C and 1-mbar pressure in a 250 ml flask for 1 h, Formamidinium iodide powder was synthesized. The resulting products were dissolved in ethanol, recrystallized from diethyl ether, and finally dried at RT in a vacuum oven for 24 h. Using this synthesized FAI, FAPbI3 powder was created in a 70-mL vial by mixing it 1:1 with lead iodide in 11 ml of 2-methoxyethanol by stirring. The resulting mixture was heated to 120°C and then precipitated by retrograde method. The FAPbI3 powder was baked for 30 min at 150°C.
Method: UV-Vis spectroscopy
Description: The optical properties of the films were measured using UV-Vis spectroscopy (Shimadzu UV-2600).