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

NiO is widely used for hole-transporting layers in p-i-n-type perovskite solar cells (PSCs) due to its stability, wide bandgap (≈3.5 eV), and solution processability. However, during solution processing, oxygen exposure can induce non-stoichiometry, forming Ni.