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) 2 PbBr 4 ( 1, 2-FBA = 2-fluorobenzylamine) as the parent compound, a unique multilayered alternating cations intercalation (MACI) perovskite (2-FBA)(MA) 2 Pb 2 Br 7 ( 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 × 10 14 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.