Facile Surface Engineering of Nickel Oxide Thin Film for Enhanced Power Conversion Efficiency of Planar Heterojunction Perovskite Solar Cells

One of the key strategies for improving photovoltaic performance of perovskite solar cells is to optimize the charge transport/recombination behaviors at the interfaces of the device. Here, we demonstrate a facile but effective method for surface engineering of nickel oxide thin film, which enables improved film morphology with the optimal electronic states allowing substantial reduction of defects between the interface of perovskite and the hole transport layer. As a result, a substantial improvement in hole extraction, transport, and collection properties is achieved by the surface engineering of nickel oxide thin film, leading to the increased power conversion efficiency from 12.30% to 17.03% of the planar heterojunction perovskite solar cells. In addition, this work reveals that the improved surface properties suppress charge recombination at the interface of perovskite/nickel oxide, which is attributed to proper band alignment, superior hole extraction, and decreased resistance for charge transfer.