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

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 Pb²⁺ 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 cm²) 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 cm²), 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.