Lewis Acid–Base Coordination‐Driven Interface Passivation Using 3‐Hydroxyflavone for Inverted Perovskite Solar Cells

ABSTRACT Interface recombination and long‐term instability under illumination remain major barriers to the large‐scale application of perovskite solar cells. To address these issues, we developed an interfacial passivation strategy using 3‐hydroxyflavone (3‐HF), which functions through Lewis acid–base coordination. The strong Lewis acidity of Pb 2+ allows it to compete with the intramolecular hydrogen bonds of 3‐HF for the carbonyl coordination site, forming a stable structure that effectively suppresses interface defects and increases the ion‐migration barrier. In addition, this passivation layer optimizes the energy‐level alignment at the interface, thereby promoting effective electron extraction and transport. The small‐area (0.09 cm 2 ) perovskite solar cell device fabricated with the 3‐HF passivation strategy achieved a champion power conversion efficiency (PCE) of 26.6%. Crucially, it also enhances the performance and stability of the mini‐modules (14 cm 2 ), achieving a PCE of 22.6% and maintaining 98.9% of its initial performance after continuous illumination for 500 h. This research takes an important step toward scalable manufacturing of perovskite solar modules.