Engineering Buried Interfaces With a π ‐Ionic Lock for Efficient Perovskite Solar Cells

Meticulous design of buried interfaces is crucial for achieving efficient and stable inverted perovskite solar cells (PSCs), as they have a crucial impact on perovskite crystallization, charge transport, and degradation pathways. Herein, we introduce a π ‐ionic lock interlayer, 1‐benzyl‐3‐methylimidazolium hexafluorophosphate (BzMIMPF 6 ), that simultaneously strengthens interfacial electronic coupling and chemically passivates defects at the hole‑transport‑layer (HTL)/perovskite buried interface. Strong π ‐ π interactions between the carbazole units of Me‐4PACz and the benzyl‐imidazolium (BzMIM + ) aromatics enhance electronic coupling at the perovskite/HTL interface. Concurrently, PF 6 − anions effectively passivate iodine vacancies and form ion pairs with uncoordinated FA + , MA + , and Pb 2 + . BzMIM + further interacts with the perovskite lattice via N‐H···N hydrogen bonding to FA + /MA + cations and coordination with Pb 2+ . The resulting π ‐ionic lock interlayer provides a defect‐minimized template for perovskite crystallization, accelerates hole extraction, and suppresses trap‐assisted recombination. Consequently, the device with π ‐ionic lock interlayer achieves a power conversion efficiency of 26.70% (certified 26.64%), and unencapsulated device retains over 90% of their initial efficiency after ∼2200 h of storage under low‐humidity conditions (20°C, 20% RH). This combined supramolecular‐ionic interfacial strategy offers a scalable route to high‑performance, long‑lived inverted PSCs.