Starting materials: formamidine acetate, hydroiodic acid (HI, 57 wt% in water), lead iodide, 2-methoxyethanol (anhydrous 99.8%)
Product: thin film
Description: By reaction of 20 mg 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 synthesized 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. A small amount of MADCl2 was incorporated.
Method: UV-Vis spectroscopy
Description: The absorption spectrum was measured using Shimadzu UV-2600.