Zero-Dimensional Lead-Free FABiI Single Crystals for High-Performance X-ray Detection.

Direct X-ray detectors based on metal halide perovskites and their derivatives exhibit high sensitivity and low limit of detection (LoD). Compared with three-dimensional (3D) hybrid lead halide perovskites, low-dimensional ABiI perovskite derivatives (A = Cs, Rb, NH, CHNH(MA)) present better stability, greater environmental friendliness, and comparable X-ray detection performance. Here, we report FABiI (FA= CH(NH)) single crystals (SCs) as a new member of the ABiI series for X-ray detection, which were prepared by the nucleation-controlled secondary solution constant temperature evaporation (SSCE) method. Centimeter-sized FABiI SCs show a full width at half-maximum (fwhm) of 0.0096°, which is superior to that of recently reported CsBiI (0.058°) and MABiI SCs (0.024°) obtained by inverse temperature crystallization (ITC). The as-grown FABiI SC shows a large resistivity of 7.8 × 10 Ω cm and a high ion migration activation energy () of 0.56 eV, which can guarantee a low noise level and good operational stability under a large external bias. The FABiI SC detector exhibits a LoD of 0.2 μGy s, a sensitivity of 598.1 μC Gy cm , and an X-ray detection efficiency of 33.5%, which are much better than those of the commercialized amorphous selenium detector. Results presented here will provide a new lead-free perovskite-type material to achieve green, sensitive, and stable X-ray detectors.