Methylammonium bromine

Unless the special statement, all materials were purchased from Sigma-Aldrich or TCI and used without further purification. The SnO₂ solution was purchased from Alfa Aesar (tin (IV) oxide, 15 wt% in H₂O colloidal dispersion). Dimethylformamide (DMF, 99.8%), dimethyl sulfoxide (DMSO, 99.7%), ethyl acetate (EA, 99.8%) and Chlorobenzene (CB, 99.8%) were purchased from Acros; 4-tert-butyl pyridine (tBP, 96%), lithium bistrifluorosulfonyl imide (LiTFSI, 99.95%), lead iodide (PbI₂, 99.99%) and lead bromine (PbBr₂, 99%) were purchased from TCI. Methylammonium iodide (MAI), methylammonium chloride (MACl), methylammonium bromine (MABr) and 2,2′,7,7′-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-MeOTAD, 99.5%) were purchased from Xi'an Polymer Light Technology Corp. Indium tin oxide (ITO, Transmission>95%) substrates were purchased from South China Science & Technology Company limited.

Formamidinium iodide (FAI, 99.99%), methylammonium bromine (MABr, 99.99%), lead iodide (PbI₂, 99.99%), lead bromide (PbBr₂, 99.99%), BCP (99.99%), and PTAA (M_n = 3200, M_w = 4900) were purchased from Xi'an Polymer Light Technology Corp., China. Buckminsterfullerene (C₆₀) was purchased from Xiamen Funano New Material Technology Corp., China. [6,6]‐Phenyl‐C61‐butyric acid methyl ester (PC₆₁BM, 99.99%) was purchased from Nano‐C Tech., USA. Chlorobenzene (CB), DMF, and DMSO were purchased from Tokyo Chemical Industry. Cesium iodide (CsI) and EA were purchased from Alfa Aesar.