Naphthalenediimide/Iodobismuthate Hybrid Heterostructures: Water Resistance and Long-Lived Charge-Separated States

Organic-inorganic hybrid iodobismuthate perovskites have become promising semiconductive materials for their environmentally friendly and light-harvesting characteristics. However, their low-dimensional bismuth-iodide skeletons result in poor charge-separation efficiency, limiting their application in optoelectronic devices. To address this issue, the donor-acceptor (D-A) heterostructures have been introduced to the iodobismuthate hybrid materials by incorporating an electron-deficient N,N'-bis(4-aminoethyl)-1,4,5,8-naphthalene diimide (NDIEA) as the electron acceptor and organic counterpart. Five naphthalenediimide/iodobismuthate hybrid heterostructures, named (H₂NDIEA)_1.5·Bi₂I₉·3DMF (1), H₂NDIEA·[Bi₂I₈(DMF)₂]·2DMF (2), (H₂NDIEA)₂·Bi₄I₁₆·2H₂O·4MeOH (3), (H₂NDIEA)₂·Bi₄I₁₆·8H₂O (4), and [(H₂NDIEA)₂·Bi₆I₂₂]·4nH₂O (5) (DMF = N,N-dimethylformamide), were synthesized. Their crystal structures, water stabilities, charge-separated behaviors, and electrical properties have been studied through experimental and computational investigations. The results revealed that hybrids 3-5 exhibited high water resistance attributed to their tightly packed structures and robust H-bonds between solvent molecules and organic-inorganic supramolecular frameworks. Density functional theory calculations confirmed characteristic type-IIa band alignments of all the five hybrids, facilitating to the photoinduced charge separation. Moreover, the closer contact caused by the strong anion-π interactions between electron donors and acceptors in hybrid 5 leads to the long-lived charge-separated states and improved electrical properties compared to the other hybrids.