“…Indium tin oxide (ITO) (the sheet resistance was 10 ohm sq −1 , and the transmittance was more than 85%) was purchased from Advanced Election Technology Co., Ltd. Methylamine iodide (CH 3 NH 3 I, 99.0%), methylamine chloride (CH 3 NH 3 Cl, 99.0%), lead(II) iodide (PbI 2 , 99.0%), lead(II) chloride (PbCl 2 , 99.0%), [6,6]-phenyl-C 61 -butyric acid methyl ester (PC 61 BM), poly-[bis(4phenyl)(2,4,6-trimethylphenyl)amine] and poly (ethylene imine) (PEI) were purchased from Xi'an Polymer Light Technology Corp. N,N-Dimethylformamide (DMF, AR), dimethyl sulfoxide (DMSO, AR), methylamine (33 wt% in absolute ethanol), anhydrous acetonitrile (ACN, 99.8%), gamma-butyrolactone (GBL, 99%), chlorobenzene (CB, anhydrous, 99.8%), and isopropanol were purchased from Sigma-Aldrich. Acetone (AR) and ethanol (AR) were purchased from Beijing Chemical Works.…”