Abstract
X-rays are widely used in probing inside information nondestructively, enabling broad applications in the medical radiography and electronic industries. X-ray imaging based on emerging lead halide perovskite scintillators has received extensive attention recently. However, the strong self-absorption, relatively low light yield and lead toxicity of these perovskites restrict their practical applications. Here, we report a series of nontoxic double-perovskite scintillators of Cs2Ag0.6Na0.4In1-yBiyCl6. By controlling the content of the heavy atom Bi3+, the X-ray absorption coefficient, radiative emission efficiency, light yield and light decay were manipulated to maximise the scintillator performance. A light yield of up to 39,000 ± 7000 photons/MeV for Cs2Ag0.6Na0.4In0.85Bi0.15Cl6 was obtained, which is much higher than that for the previously reported lead halide perovskite colloidal CsPbBr3 (21,000 photons/MeV). The large Stokes shift between the radioluminescence (RL) and absorption spectra benefiting from self-trapped excitons (STEs) led to a negligible self-absorption effect. Given the high light output and fast light decay of this scintillator, static X-ray imaging was attained under an extremely low dose of ∼1 μGyair, and dynamic X-ray imaging of finger bending without a ghosting effect was demonstrated under a low-dose rate of 47.2 μGyair s−1. After thermal treatment at 85 °C for 50 h followed by X-ray irradiation for 50 h in ambient air, the scintillator performance in terms of the RL intensity and X-ray image quality remained almost unchanged. Our results shed light on exploring highly competitive scintillators beyond the scope of lead halide perovskites, not only for avoiding toxicity but also for better performance.
Highlights
X-ray imaging has been actively utilised in the fields of industrial material inspection, medical diagnosis and scientific research[1,2,3,4,5,6,7,8,9,10]
Current Xray imaging systems mostly rely on scintillators that are capable of converting X-ray photons into visible photons that are detected by a photodiode array[13,14,15]
BIIICl6 is regarded as a homologue of the ABX3-type perovskite, in which the B sites are replaced by equal amounts of monovalent and trivalent cations[40]
Summary
X-ray imaging has been actively utilised in the fields of industrial material inspection, medical diagnosis and scientific research[1,2,3,4,5,6,7,8,9,10]. Current Xray imaging systems mostly rely on scintillators that are capable of converting X-ray photons into visible photons that are detected by a photodiode array[13,14,15]. Conventional scintillators, such as thallium-doped caesium iodide (CsI:Tl)[16,17] and cerium-doped lutetium−aluminium garnet (LuAG:Ce)[18], usually require expensive and time-consuming synthesis, which poses a major challenge for device processability. The emerging lead halide perovskites for X-ray detectors are starting to show attractive merits of facile fabrication, fast response and good spatial resolution[19,20,21,22,23,24,25,26]. The relatively low X-ray light yield, lead toxicity[27,28,29] and instability greatly limit their applications in high-end X-ray imaging featuring low-dose exposure, hazard-free manufacturing, real-time monitoring and robustness
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