Viologen Enabled Dynamic Interface Passivation for Efficient and Stable Inverted Perovskite Solar Cells

ABSTRACT Interfacial defects constitute major non‐radiative recombination centers, thereby constraining the open‐circuit voltage (V OC ), the power conversion efficiency (PCE), and the stability of the perovskite solar cells (PSCs). Conventional passivation approaches are predominantly static; in contrast, we introduce a dynamic interfacial‐modulation strategy employing methyl viologen (MV), a bipyridyl molecule that can reversibly shuttle between its dicationic (MV 2+ ) and radical‐cationic (MV +• ) redox states. This redox flexibility allows MV to autonomously heal newly formed Pb 0 and I 0 defects in situ during operation: MV 2+ oxidizes Pb 0 back to Pb 2+ , while the concomitantly generated MV +• reduces I 0 to I − . Together, these processes effectively suppress interfacial non‐radiative recombination. Implementation of the MV interlayer yields a champion PCE of 26.44% with a V OC of 1.167 V and a fill factor of 85%, representing one of the highest efficiencies reported for inverted PSCs. Under AM 1.5 G maximum power point tracking, the MV‐modified devices retain 90% of their initial efficiency after 1,000 h of continuous illumination. This work establishes viologen derivatives as a versatile class of redox‐active interfacial modifiers for perovskite photovoltaics and provides new insights into the concurrent management of defect passivation and charge‐carrier dynamics in complex optoelectronic architectures.