New Hybrid Hole Extraction Layer of Perovskite Solar Cells with a Planar p-i-n Geometry

We report a highly efficient p-i-n type planar perovskite solar cell with a hybrid PEDOT/NiO_x hole-extraction layer. It has been found that the perovskite solar cell with a NiO_x thin film as a hole-extraction layer generally exhibits lower fill factor compared to the conventionally used PEDOT:PSS thin film, whereas it shows higher photocurrent and photovoltage. The fill factor of the NiO_x-based perovskite solar cell can be significantly improved by treating the NiO_x surface with a dilute PEDOT solution. The photoluminescence quenching study and impedance spectroscopic (IS) analysis have revealed that the hole injection at the perovskite/NiO_x interface is significantly facilitated with the PEDOT treatment, which should lead to the increased fill factor. As a result, the p-i-n type planar perovskite solar cell with the new hybrid hole-extraction layer exhibits a high conversion efficiency of 15.1% without the hysteresis effect.