High concentration PbI 2 ·DMSO complex precursor solution of 1.7 M in DMF for high-thickness and full-coverage CH 3 NH 3 PbI 3−x Br x thin films

Abstract

To prepare the high-thickness and Br-doping CH3NH3PbI3 − xBrx thin film, the high concentration (1.7 M) PbI2·DMSO complex precursor solution in DMF was successfully prepared by repeating the cycle of PbI2-dissovling and DMSO-adding. The influence of PbI2·DMSO complex precursor solution concentration on the formation and conversion of the PbI2·DMSO complex thin film was investigated by X-ray diffraction, ultraviolet–visible spectroscopy, ultraviolet–visible-near infrared spectroscopy and scanning electron microscope. The CH3NH3PbI3 − xBrx thin films with the thickness of 337, 446 and 529 nm were obtained by spin-coating 1.3, 1.5 and 1.7 M PbI2·DMSO complex precursor solutions in DMF and subsequently being converted by 0.465 M isopropanol solution of the methylammonium halide mixture with the molar ratio of CH3NH3I/CH3NH3Br = 85/15. The planar perovskite solar cell with the 529 nm-thick CH3NH3PbI3 − xBrx thin film gave the best and the average photoelectric conversion efficiency of 12.83% and 11.55 ± 1.28% at the relative humidity of 50–54% under the illumination of simulated AM 1.5 sunlight (100 mW cm− 2).