Oxidation State Manipulation of NiOx for High Performance and Light-Soaking Stability of Perovskite Solar Modules

Abstract

NiOx is widely used for hole-transporting layers in p-i-n-type perovskite solar cells (PSCs) due to its stability, wide bandgap (approximate to 3.5 eV), and solution processability. However, during solution processing, oxygen exposure can induce non-stoichiometry, forming Ni >= 3 +. While Ni >= 3 + enhances hole mobility, it also promotes redox reactions at the interface, undermining long-term stability. To utilize the improved mobility without sacrificing stability, bilayer NiOx films with controlled Ni >= 3 + concentrations can be fabricated. Sputtering is ideal for this, enabling precise control of oxygen partial pressure during deposition. This study utilizes sputtering to regulate Ni >= 3 + levels and optimize the ratio of two NiOx layers in bilayer films, improving charge extraction and transport. A fabricated perovskite module with a 16.0 cm2 aperture area achieves a photo-conversion efficiency (PCE) of 16.5%. Additionally, the module retains 80% of its initial PCE after 1000 h under continuous 1-sun illumination, thanks to the stable bilayer NiOx structure.