Iodine-assisted antisolvent engineering for stable perovskite solar cells with efficiency >21.3 %

The quality of the photoactive film is a significant factor in determining the power conversion efficiency (PCE) and the stability of perovskite solar cells (PSCs). We report a simple upgraded antisolvent washing treatment using iodine modulation, which significantly improves the MAPbI3 films with high crystallinity and chemical uniformity. A detailed model for improving the mechanism is proposed to describe how the upgraded antisolvent enhances both the perovskite crystallization and passivates the under-coordinated Pb2+ dangling bond. PSCs fabricated with the FTO/TiO2/MAPbI3/Spiro-OMeTAD/Ag architecture used high quality films with less defective surfaces, present a PCE of 21.33%, retaining 91% of its initial value in ambient without any encapsulation after 30 days. These results provide insight into the surface defect passivation process achieved by halide ions balance while providing a simple and efficient process that can be extensively used to fabricate high-quality perovskite films.