2D Multilayered Perovskite Ferroelectric with Halogen Bond Induced Interlayer Locking Structure toward Efficient Self‐Powered X‐Ray Detection

Abstract 2D Ruddlesden‐Popper (RP) hybrid perovskite ferroelectrics have emerged as a promising class of direct X‐ray detection materials. However, their intrinsic van der Waals gaps result in weak interlayer interactions that destabilize the layered motifs impacting the stability of the X‐ray detector. Thus, it is crucial but remains toughly challenge to enhance interlayer interactions exploring stable RP perovskite ferroelectric X‐ray detectors. Here, halogen bond is proposed to enhance the interlayer interactions of RP perovskite ferroelectrics obtaining a 2D trilayered ferroelectric, (BrPA) 2 (EA) 2 Pb 3 Br 10 ( BEPB , BrPA = 3‐bromopropylaminium; EA = ethylammonium). Strikingly, the strong Br···Br halogen bonds lock cations to the inorganic skeletons, and C─H···Br hydrogen bonds bridge adjacent spacing sheets, which effectively improves structural stability and suppresses ion migration. The typical P‐E hysteresis loops reveal its concrete ferroelectric behaviors, giving a large polarization of ≈7.3 µC cm −2 . Consequently, the BEPB ‐based X‐ray detector results in a high sensitivity of 562.6 µC Gy −1 cm −2 at 0 V bias, and most importantly, it exhibits low baseline drift and exceptional environmental stability. As far as is known, halogen bond strengthening 2D multilayered ferroelectric to achieve stable and efficient X‐ray detection is unprecedented, which sheds light on the future design of stable optoelectronic devices toward practical applications.