Review of Defect Passivation for NiO_x-Based Inverted Perovskite Solar Cells

In recent years, organic–inorganic hybrid perovskite solar cells (PSCs) have attracted extensive attention due to their high power conversion efficiency (PCE) and simple preparation process. The selection and optimization of the hole transport layer (HTL) are very important for device performance. Compared to other HTLs, nickel oxide (NiO x ) has been widely used in PSCs due to its good chemical stability, high hole mobility, and simple preparation method. This review begins with the application of NiO x HTL in planar PSCs and systematically introduces the influence of the structure and photoelectrical properties of devices by doping and surface modification. The effects of NiO x modification on the power conversion efficiency (PCE), filling factor (FF), open-circuit voltage ( V oc ), short-circuit current ( J sc ), and stability of PSCs are reviewed in detail from the perspectives of energy-level matching, hole mobility, and crystallinity. Finally, the future of NiO x -based planar PSCs is discussed.