Suppressing Interfacial‐Accelerated Degradation in Perovskite Solar Cells via Supramolecular Co‐Assembly

Metal halide perovskites exhibit exceptional optoelectronic properties, but the perovskite/organic hole‐transport layer interface often accelerates device degradation under thermal and illumination stress. Single‐component interlayers are insufficient to prevent this coupled interfacial failure, leading to simultaneous destabilization of both the perovskite absorber and doped Spiro‐OMeTAD. Here, we report a carbazole‐derived supramolecular co‐assembly composed of ammonium‐functionalized (CzPACl) and flexible oligo(ethylene glycol) (CzOEG) monomers that simultaneously passivates the perovskite surface and stabilizes the adjacent Spiro‐OMeTAD layer. The resulting nanosheet interlayer suppresses non‐radiative recombination, mitigates ionic migration, and preserves the concentration of Spiro‐OMeTAD radical cations, enhancing interfacial wettability and mechanical compliance. Perovskite solar cells incorporating this co‐assembled layer achieve a power conversion efficiency (PCE) of 25.8% and retain over 90% of their initial efficiency after 1000 h of continuous illumination or over 80% after 1000 h of aging at 85°C. This work highlights supramolecular co‐assembly as a rational strategy to suppress coupled interfacial degradation pathways, providing a general approach for stabilizing perovskite optoelectronic devices.