Preparation of 596 nm-thick and full-coverage CH3NH3PbI3−xBrx thin films using 1.9 M PbI2·NMP complex solution in DMF

Abstract

The high concentration of 1.9 M PbI2·NMP complex precursor solutions in DMF were successfully prepared by repeating the cycle of PbI2-dissolving and NMP-adding. 596 nm-thick CH3NH3PbI3−xBrx thin films were obtained by spin-coating 1.9 M PbI2·NMP complex precursor solution in DMF and subsequently being converted by 0.535 M isopropanol solution of the methylammonium halide mixture with the molar ratio of CH3NH3I/CH3NH3Br = 85/15. The planar perovskite solar cells based on the 596 nm-thick CH3NH3PbI3−xBrx thin films exhibited the best photoelectric conversion efficiency (PCE) of 12.13% and the average PCE of 11.90 ± 0.40% at the relative humidity of 50–54% under the illumination of simulated AM 1.5 sunlight (100 mW cm−2).