Efficiency and stability enhancement of polymer solar cells using multi-stacks of C60/LiF as cathode buffer layer

► Multi-stacked C60/LiF is used as cathode buffer layer (CBL) in polymer solar cells. ► Device with five-stacked C60/LiF CBL shows a 19% higher PCE than LiF-only device. ► Five-stacked C60/LiF film exhibits a good conductivity due to the mixed morphology. ► High PCE of five-stacked C60/LiF device is insensitive to the thickness ratio between C60 and LiF. ► Five-stacked C60/LiF devices show superior stability compared to LiF-only devices.