Tunable Br-doping CH3NH3PbI3−xBrx thin films for efficient planar perovskite solar cells

Abstract

In this paper, the relationship of the Br contents in precursor solutions of the CH3NH3Br/CH3NH3I mixture and in the resulting CH3NH3PbI3−xBrx thin films was systemically explored and the tunable Br-doping CH3NH3PbI3−xBrx thin films were successfully obtained by the sequential deposition methods. The influence of CH3NH3Br content in the methylammonium halide mixture solutions on the chemical composition, optical absorption, crystal phase and morphology of CH3NH3PbI3−xBrx thin films and the photovoltaic performance of the corresponding planar perovskite solar cells were investigated. The result revealed that the Br contents in CH3NH3PbI3−xBrx thin films linearly increased with the increase of Br contents in the methylammonium halide mixture solutions. The planar perovskite solar cell based on the high crystallinity and less grain boundary CH3NH3PbI3−xBrx thin films using the methylammonium halide mixture solutions with the molar ratio of CH3NH3Br/CH3NH3I = 10/90 achieved a best photoelectric conversion efficiency (PCE) of 14.88% with an open-circuit voltage (Voc) of 1.03 V, a short-circuit photocurrent density (Jsc) of 20.62 mA cm−2 and a fill factor (FF) of 0.70 and an average PCE of 14.21 ± 0.67% with Voc of 1.02 ± 0.02 V, Jsc of 20.67 ± 0.15 mA cm−2 and FF of 0.67 ± 0.05.