Multilayered Alternating Cations Intercalation Perovskite Single Crystals with Strong π–π Interactions Unlock nW-Level Weak-Light Detection and Imaging

Weak-light detection and imaging are essential in monitoring, medical imaging, and military applications. Recently, metal halide perovskites are promising for optoelectronic applications owing to their outstanding semiconductor properties. However, nW-level weak-light detection and imaging remain challenging due to restricted interlayer charge transport and high dark current noise. Herein, using (2-FBA)2PbBr4 (1, 2-FBA = 2-fluorobenzylamine) as the parent compound, a unique multilayered alternating cations intercalation (MACI) perovskite (2-FBA)(MA)2Pb2Br7 (2, MA = methylamine) is obtained by introducing MA cations, which exhibits strong π–π interactions (3.177 Å) and short interlayer spacing (7.438 Å). Benefiting from the strong interlayer coupling interactions, the photodetector based on 2 exhibits an extremely low detection limit (82 nW cm–2), a remarkable responsivity (0.32 A W–1), and a high detectivity (2.01 × 1014 Jones). Impressively, clear images were successfully obtained under 82 nW cm–2. This study underscores the enormous potential of MACI perovskites for high-performance photodetectors and weak-light imaging.