image: X-ray detection down to nanograys per second by zero-dimensional MA3Bi2I9 single crystals
Sensitive X-ray detectors are essential for medical radiography, industrial inspection and security screening. However, commercially available X-ray instruments require high dosages for imaging. Further lowering the radiation dose will reduce health risks to patients; and will also increase the frequency with which X-ray images can safely be acquired, ultimately paving the way toward truly personalized patient care.
Researchers from China Academy of Engineering Physics, Nanjing University and University of Victoria demonstrated ultra-sensitive and stable X-ray detectors by using a new kind of 0D MA3Bi2I9 single-crystals. The disconnecting of the (Bi2I9)3- units in the lattice leads to a high activation energy (Ea) for ion migration (0.46 eV) and is also accompanied by a low dark carrier concentration (~ 10 6 cm-3). The suppressed ion migration and lowered dark carrier concentration enable the desirable combination of high sensitivity, low LoD, and stable operation. X-ray detectors with a low LoD of 0.62 nGyair s-1 was achieved with a 100 kVp tungsten-target X-ray tube, which approaches the background radiation on Earth (~0.1 nGyair s-1), and is significantly lower than the dose rate required for X-ray diagnostics (5.5 μGyair s-1). Additionally, the reported X-ray sensitivity of 10,620 μC Gyair-1 cm-2 is comparable to the values obtained in 3D perovskite detectors (1.1 × 10 4 μC Gyair-1 cm-2 for MAPbI3 and 2.1 × 10 4 μC Gyair-1 cm-2 for hybrid MAPbBr3/Si) and 2D perovskite detectors (8,400 μC Gyair-1 cm-2 for (NH4)3Bi2I9). It is worth noting that, unlike 2D hybrid Bi halide perovskites that cannot obtain low LoD and high sensitivity in the same direction, 0D MA3Bi2I9 X-ray detectors achieve simultaneously low LoD and high X-ray sensitivity in the out-of-plane transport mode. The 0D perovskite X-ray detectors exhibit stable operation even under high applied biases up to 120 V. No deterioration in detection performance was observed following an X-ray irradiation dose of ~23,800 mGyair, equivalent to > 200,000 times of the dose used in acquiring commercial X-ray chest radiographs.
The advance presented herein provides a promising X-ray detector candidate in X-ray imaging and medical applications. This work was published in Journal of Energy Chemistry.