Hydriodic acid

MAI was synthesised via the chemical reaction of 27 ml methylamine solution (CH₃NH₂, 40 wt.% in methanol, TCI) with 30 ml of hydriodic acid (HI 57 wt.% in water, Aldrich) in an ice bath for 2 h. The methylamine solution was added first into the round-bottom flask and then HI was dropwise added in during stirring. MAI precipitates were collected after the solution was transformed into a rotary evaporator and heated at 50 °C for 1 h. The white precipitates were washed three times with diethyl ether and finally dried in vacuum for 24 h. The PbI₂ solution was prepared by dissolving 1 mole PbI₂ in 1 ml DMF solvent and stirred at 70 °C and then 20 μl of DIO was added into the solution to promote the dissolution of PbI₂. The PbI₂ solution became clear after continuously stirring at 70 °C for overnight. Thereafter, 1.0 wt.% MAI solution was then produced by adding MAI in 2-propanol and stirred for 10 min at 50 °C. The PTB7 and PCBM solution were respectively prepared by dissolving 4 mg and 30 mg of PCBM in 1 ml of chlorobenzene. 2 mg of BCP was dissolved in 1 ml of methanol to form the BCP solution. The Al4083 PEDOT:PSS solution was used as received from Ossila (1.3 to 1.7 wt.% water solution).

Methylamine (35 mL, 40% in water, TCI) and hydriodic acid (50 mL, 57 wt% in water, Aldrich) were reacted in a 250 mL round-bottom flask at 0 °C for 2 h under magnetic stirring. The precipitate was recovered by evaporation at 50 °C for 1 h. The product was then dissolved in ethanol (anhydrous 99.9%, Samchun pure chemical co., ltd.) recrystallized from diethyl ether (99.0%, Samchun pure chemical co., ltd.) and finally dried at room temperature in a vacuum oven for 24 h. 1 M of MAPbI₃ perovskite solution was prepared by mixing the synthesized MAI powder (0.318 g) and PbI₂ (0.924 g, 99%, Aldrich) in a mixture of γ-butyrolactone (1.4 mL, Aldrich) and dimethyl sulfoxide (0.6 mL, Aldrich) at 60 °C for 30 min.