Achieving Highly Efficient and Stable Inverted Perovskite Solar Cells through Synergistic Bimolecular Interface Defect Passivation

Phenethylammonium iodide (PEAI) has been widely explored as an effective interfacial passivator in perovskite solar cells (PSCs). However, its high reactivity with perovskite promotes the formation of 2D/quasi-2D structures, and the complexity of mixed phases may trigger phase transitions, thereby undermining device stability. In this study, three-dimensional bowl-shaped carboxymethyl-β-cyclodextrin (CM-β-CD) supramolecules were introduced to suppress the deprotonation of PEAI. This approach effectively inhibits the formation of 2D perovskites and enhances device stability. CM-β-CD contains abundant functional groups that coordinate with undercoordinated Pb2+ ions via Lewis acid–base interactions, further passivating surface defects. Moreover, it was demonstrated that CM-β-CD immobilizes Pb2+ ions, effectively preventing lead leakage when the devices are immersed in water. The optimized device achieved a power conversion efficiency (PCE) of 26.06%, which is significantly higher than the 23.75% achieved by the control group. Stability was also improved, with the optimized device retaining 91.2% of its initial PCE after 1050 h of storage at 25 °C and a relative humidity of 25–35%.