Coaxial Perovskite Single‐Crystal Fiber Enables Self‐Driven, High‐Sensitivity X‐Ray Detection With Multichannel Spectral Sensing

ABSTRACT Vertical architectures are widely used in perovskite X‐ray detectors, but increasing the absorber thickness to enhance photon absorption generally lengthens the carrier‐transport path and compromises charge collection. Here, coaxial perovskite single‐crystal‐fiber X‐ray detectors are demonstrated, in which the axial photon‐absorption path is geometrically decoupled from the radial carrier‐transport distance. The optimized Ti/TiO 2 /MAPbBr 3 /PTAA/Au architecture combines this geometric decoupling with selective carrier‐transport interfaces, enabling high sensitivity and stable operation over 24 h. The asymmetric electron‐ and hole‐selective interfaces establish a built‐in electric field for carrier separation at zero external bias, while reducing the fiber diameter further shortens the radial transport distance and decreases the extent of the irradiation‐induced weak‐field region, thereby enhancing carrier collection under self‐driven operation. The optimized detector reaches an area‐normalized sensitivity of 6.2 × 10 4 µC Gy air −1 cm −2 at 15 V, while the 400‐µm‐diameter device achieves 2.5 × 10 3 µC Gy air −1 cm −2 at zero bias. A proof‐of‐concept 5 × 3 detector array assembled from individual coaxial fibers demonstrates the feasibility of array‐based X‐ray imaging. In addition, axial multielectrode segmentation provides depth‐dependent multichannel responses, enabling proof‐of‐concept discrimination among the calibrated Al/Cu/Pb attenuation conditions investigated in this study.