Optimizing Composition and Morphology for Large-Grain Perovskite Solar Cells via Chemical Control

We report solid iodine as a precursor additive for achieving purified organometallic perovskite crystals. By adding iodine, we found that the reaction can be pushed toward pure iodine phase rather than the kinetically favored chlorine phase. This approach can be applied in large crystalline perovskite solar cells and improved the average efficiency from 9.83% to 15.58%.