Co-Assembled Hybrid Interlayer Engineering for Enhanced Upper Interface Stability in Inverted Perovskite Solar Cells

Engineering electron transport layer (ETL) interface is critical for high-efficiency and long-term stability in inverted perovskite solar cells (PSCs), yet co-assembled hybrid interlayer are rarely explored for this upper interface. This work integrates 4-aminobenzoate acid hydrochloride (4AA) with a dibenzo-18-crown-6 (DB18C6) to construct a hybrid interlayer at ETL interface. The 4AA molecules intercalate into DB18C6 aggregates, homogenizing the monolayer and boosting surface coverage (from 0.57 to 0.79) and strengthening the interfacial dipole moment (from 2 to 7 Debye). This interlayer provides dual passivation, in which the ─NH₃ ⁺ and ─COOH groups of 4AA neutralize ionic defects, while DB18C6 optimizes perovskite crystallinity and energy level alignment. Therefore, modified devices achieve an efficiency of 26.33% (exceeding 22.92% of the control) with high open-circuit voltage (V_OC) of 1.167 V and fill factor (FF) of 86.05% (compared to 1.130 V and 80.38% of the control). More importantly, the co-assembled hybrid interlayer serves as a barrier against environmental and ionic degradation. The unencapsulated device demonstrates outstanding operational stability, retaining 93.2% of initial efficiency after 1000 h of maximum power point tracking. This work demonstrates a co-assembly strategy to address efficiency and stability challenges at ETL interface, paving a reliable path toward high-performance and stable inverted PSCs.