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.