Ultralow Detection Limit and Robust Hard X-ray Imaging Detector Based on Inch-Sized Lead-Free Perovskite Cs3Bi2Br9 Single Crystals

Halide perovskites are promising candidates for soft X-ray detection (<80 keV) owing to their high X-ray absorption coefficient, resistivity, and mobility lifetime product. However, the lack of large high-quality single crystals (SCs) renders it challenging to manufacture robust hard X-ray imaging systems (>100 keV) with a low detection limit and stable dark current. Herein, high-quality inch-size two-dimensional (2D) Cs₃Bi₂Br₉ (CBB) single crystals are grown from a melt via the Bridgman method. The crystal quality is enhanced by eliminating inclusions of CsBr-rich phases and restraining the trap-state density, leading to an enhanced resistivity of 1.41 × 10¹² Ω cm and a mobility lifetime product of 8.32 × 10^-4 cm² V^-1. The Au/CBB/Au single-crystal device exhibits a high sensitivity of 1705 μC Gy_air^-1 cm^-2 in all-inorganic bismuth-based perovskites and an ultralow detection limit of 0.58 nGy_air s^-1 in all of the bismuth-based perovskites for 120 keV hard X-ray detection. The CBB detector exhibits high work stability with an ultralow dark current drift of 2.8 × 10^-10 nA cm^-1 s^-1 V^-1 and long-term air environment reliability under a high electric field of 10 000 V cm^-1 owing to the ultrahigh ionic activation energy of the 2D structure. The proposed robust imaging system based on CBB SC is a promising tool for X-ray medical imaging and diagnostics.