Effects of Bromide-mixing in Methylammonium Lead Iodide on Photovoltaic Properties of ZnO-based Perovskite Solar Cells

Abstract

To improve efficiency of ZnO-based perovskite solar cells, a mixture iodide-bromide (I-Br) of FA0.4MA0.6Pbl3-2xBr2x perovskite structure was prepared by two-step sequential deposition method and used as photo absorber layer. Solar cells with structure of ITO/ZnO/PCBM/perovskite/P3HT/Au were fabricated and characterized. The perovskite films were prepared by mixing precursor PbI2 and PbBr2 at various molar ratio. It was found that the grain sizes and crystallite sizes of perovskite crystal were comparable for different Br doping. The existence of Br ions in perovskite layer was confirmed. In addition, the increase in band gap energy was observed. The highest average power conversion efficiency (PCE) of 2.17% was achieved from the device with FA0.4MA0.6PbI2.8Br0.2 layer. This PCE value is higher than the FA0.4MA0.6PbI3 device which exhibited 1.53%-efficiency. The enhancement in PCE could be explained by the development of light absorption and charges transport.