Bilayer interfacial engineering with PEAI/OAI for synergistic defect passivation in high-performance perovskite solar cells

Abstract Interfacial defects and environmental instability at perovskite surfaces pose significant challenges for inverted perovskite solar cells (PSCs). Surface post-treatment strategies have emerged as a viable approach to improve film quality and passivate defects. Although organic molecules can passivate both surfaces and grain boundaries via hydrogen or covalent bonding, their limited adsorption specificity often results in incomplete defect neutralization. In this work, we introduce a bilayer passivation approach employing phenethylammonium iodide (PEAI) and n-octylammonium iodide (OAI) to concurrently mitigate non-radiative recombination and improve stability. PEAI passivates undercoordinated Pb 2+ at grain boundaries and surfaces, effectively eliminating deep-level traps and suppressing non-radiative losses. Meanwhile, OAI forms a hydrophobic barrier on the perovskite surface through its long alkyl chains, inhibiting moisture penetration without compromising interfacial charge transport. As a result, the perovskite film exhibits significantly enhanced optoelectronic performance and environmental stability, achieving a champion power conversion efficiency (PCE) of 24.48%.