Robust Fabrication of Hybrid Lead‐Free Perovskite Pellets for Stable X‐ray Detectors with Low Detection Limit

Abstract X‐ray detectors are widely utilized in medical diagnostics and nondestructive product inspection. Halide perovskites are recently demonstrated as excellent candidates for direct X‐ray detection. However, it is still challenging to obtain high quality perovskites with millimeter‐thick over a large area for high performance, stable X‐ray detectors. Here, methylammonium bismuth iodide (MA₃Bi₂I₉) polycrystalline pellets (PPs) are developed by a robust, cost effective, and scalable cold isostatic‐pressing for fabricating X‐ray detectors with low limit of detection (LoD) and superior operational stability. The MA₃Bi₂I₉‐PPs possess a high resistivity of 2.28 × 10¹¹ Ω cm and low dark carrier concentration of ≈10⁷ cm⁻³, and balanced mobility of ≈2 cm² V⁻¹ s⁻¹ for electrons and holes. These merits enable a sensitivity of 563 μC Gy_air⁻¹ cm⁻², a detection efficiency of 28.8%, and an LoD of 9.3 nGy_air s⁻¹ for MA₃Bi₂I₉‐PPs detectors, and the LoD is much lower than the dose rate required for X‐ray diagnostics used currently (5.5 μGy_air s⁻¹). In addition, the MA₃Bi₂I₉‐PPs detectors work stably under high working bias field up to 2000 V cm⁻¹ after sensing an integrated dose >320 Gy_air with continuous X‐ray radiation, demonstrating its competitive advantage in practical application. These findings provide an approach to explore a new generation of low LoD, stable and green X‐ray detectors based on MA₃Bi₂I₉‐PPs.