High efficiency stable inverted perovskite solar cells without current hysteresis

The inverted perovskite solar cell fabricated using a two-step method exhibited the highest FF of 0.85 and good efficiency of 18% based on CH sub(3)NH sub(3)PbI sub(3 ). A small amount of H sub(2)O was added into PbI sub(2)/DMF to make a homogenous precursor solution. A high quality PbI sub(2) film with full coverage was formed on a PEDOT:PSS surface by spin coating of the homogeneous PbI sub(2) precursor solution. The perovskite film fabricated from the high quality PbI sub(2) film is highly pure, smooth and very dense even without any pinhole. The champion cell achieves a remarkable fill factor (FF) of 0.85, which is the highest value reported in perovskite solar cells. The FF value is also very reproducible with less than 10% deviation for 50 cells. The cell exhibits no current hysteresis and is stable under both dark and illumination conditions in dry and inert atmospheres. The results not only provide a strategy to fabricate high efficiency inverted perovskite solar cells but also reveal how the water additive in the PbI sub(2)/DMF solution may affect the properties of PbI sub(2) and therefore the perovskite film prepared using the two-step method and the overall photovoltaic performance of the corresponding inverted solar cell.