2.2. Synthesis of Methylammonium Iodide and Preparation of Perovskite Solution

Methylammonium iodide (MAI) was synthesized using a methylamine solution (33 wt % in ethanol) and hydroiodic acid (57 wt % in water). First, methylamine was stirred using a dropwise addition of hydroiodic acid in an ice bath for 2 h. The solvent was evaporated by a rotary evaporator, and then the mixture was solvated in ethanol. After recrystallization with diethyl ether, the white solid was precipitated and then dried under a vacuum for 24 h. The perovskite solution was prepared with MAI and lead (II) chloride (99.999%, Sigma-Aldrich, St. Louis, MO, USA) at a 3:1 molar ratio, 45 wt %, in N,N-dimethylformamide (DMF).