Mechanical Exfoliated Flexible Lead‐Free Single‐Crystalline Perovskite Ferroelectric for Sensitive Self‐Driven X‐Ray Detection

ABSTRACT Organic–inorganic halide perovskites have emerged as promising candidates for flexible direct X‐ray detectors. As a representative green material, lead‐free halide perovskites hold significant potential for developing efficient, environmentally friendly, flexible X‐ray detectors. However, current research on flexible lead‐free perovskite X‐ray detectors is confined to polycrystalline materials, which are inherently susceptible to grain‐boundary defects and exhibit inferior charge‐transport characteristics. Here, we first mechanically exfoliate a single‐crystal flexible lead‐free ferroelectric thin film for sensitive self‐driven X‐ray detection. Specifically, 2D lead‐free (Benzylamine) 2 CsAgBiBr 7 perovskite exhibits weak interlayer interactions, facilitating mechanical exfoliation for flexible single‐crystal thin‐film devices. Remarkably, utilizing its inherent ferroelectric polarization, the single‐crystal thin film exhibits remarkable self‐powered detection, achieving a high sensitivity of 729.2 µC Gy air −1 cm −2 with stable photoelectric response after bending. This breakthrough in fabricating the first flexible lead‐free single‐crystal perovskite film detectors paves the way for the development of next‐generation wearable green radiation‐monitoring systems.