The effect of bromine doping on the perovskite solar cells modified by PVP/PEG polymer blends

In this paper, highly uniform and band gap tunable CH3NH3PbI3-xBrx perovskite film was successfully prepared by a polymer blends (Polyvinyl Pyrrolidone/polyethylene glycol) modified sequential deposition method in ambient atmosphere. Moreover, the influences of the Br content on the surface morphology, structure, optical absorption and luminescence properties of CH3NH3PbI3-xBrx films and the photovoltaic performance of the corresponding perovskite solar cells based on ZnO-TiO2 nanorod arrays were investigated. The results revealed that introducing bromine ion can decrease the convert rate from PbI2 to CH3NH3PbI3. Furthermore, bromine doping can expand the bang gap of the CH3NH3PbI3, which is benefit to the improvement of open-circuit voltage. The CH3NH3PbI3-xBrx perovskite solar cell shows the best device performance with an open-circuit voltage (Voc) of 0.87 V, a short-circuit current density (Jsc) of 17.41 mA/cm(2), fill factor (FF) of 0.6 and power conversion efficiency of 9.12% when the molar ratio of PbBr2/PbI2 = 15/85.