Modulating Dual Functionalities of Hydrazide Derivatives for Iodide Oxidation Suppression and Defect Passivation in Printable Mesoscopic Perovskite Solar Cells

Abstract The oxidation of iodide ions during annealing in air and rich defects generated at crystal terminations in perovskite are major limitations for achieving high photovoltaic performance in printable mesoscopic perovskite solar cells (p‐MPSCs). Here, the dual role of hydrazide derivatives in inhibiting iodide oxidation and passivating crystal termination defects is reported and how the dual role is affected by the substituent is studied. It's found that varying the hydrazide derivative from formylhydrazine (FH) to benzhydrazide (BH) and then to 4‐tert‐butylbenzhydrazide (TBBH) by introducing phenyl and 4‐tert‐butylphenyl substituents enhances the electron donating ability of hydrazides due to substituent electronic effect. The tailored hydrazides present enhanced iodide oxidation suppression and defect passivation capabilities, which lowers the trap density of perovskite in p‐MPSCs significantly. As the most effective additive, TBBH improves the power conversion efficiency of the p‐MPSC from 18.66% to 20.30%, and the resulted device maintains 90% of its initial efficiency after 500 h tacking at maximum power point at 55 ± 5 °C under simulated 1 sun illumination.