Customized Cyclodextrin Supramolecular Networks for Synergistic Interface Modulation of SnO ₂ Nanocrystals and Perovskite Films Toward High‐Performance Photodetectors

Small‐molecule Lewis bases have been extensively used to passivate buried interfacial defects in n‐i‐p‐structured perovskite optoelectronic devices, thereby improving their performance and stability. However, the limited anchoring sites and weak, uncontrollable coordination of prevalent small molecules restrict the ordered nucleation and crystallization of perovskite films, as well as effective defect passivation at the buried interface. Herein, β ‐cyclodextrin/citric acid (CDCA) supramolecules with abundant ─C═O and ─OH functional groups were synthesized to mitigate defects in both SnO 2 and perovskite layers through supramolecular interactions. Density functional theory calculations, corroborated by experimental data, indicate that ─C═O and ─OH functional groups exhibit preferential interactions with undercoordinated Pb 2+ sites within the perovskite lattice and oxygen vacancy‐associated defects in SnO 2 , respectively. This dual‐interfacial decoration strategy enhances the crystallinity of perovskite films and optimizes the band alignment at the buried SnO 2 /perovskite interface, further improving carrier transport efficiency. Consequently, the CDCA‐modified perovskite photodetectors (PPDs) exhibit competitive performance, including a short rise time of 20.06 µs, high detectivity of 3.5 × 10 12 Jones, and notably long‐term stability under intense laser irradiation (500 mW/cm 2 ) of 405‐nm‐line. Our work provides valuable insights into tailoring highly effective supramolecular Lewis bases with plentiful passivation sites for fabricating high‐performance and stable PPDs.