Low-dose real-time X-ray imaging with nontoxic double perovskite scintillators

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 Cs(2)Ag(0.6)Na(0.4)In(0.85)Bi(0.15)Cl(6)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 similar to 1 mu Gy(air), and dynamic X-ray imaging of finger bending without a ghosting effect was demonstrated under a low-dose rate of 47.2 mu Gy(air) s(-1). After thermal treatment at 85 degrees 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. X-ray imaging: Better crystals to convert X-rays into light Low-dose X-ray imaging, which relies on scintillators to convert X-ray photons into readily detectable photons of light, has been improved using new varieties of scintillators composed of materials known as double perovskites. Yang Yang and colleagues at Zhejiang University in China made their scintillators from nontoxic elements including caesium, silver, sodium, indium, bismuth and chloride ions. They outperform existing lead halide perovskite scintillators due to greatly increased light-yield, heat stability and low toxicity. Unlike many alternatives, they do not contain toxic lead ions. The researchers maximised the light-yielding efficiency by controlling the content of bismuth ions (Bi3+) in the double perovskite crystals. They demonstrated the potential of their material by achieving exceptionally low-dose static X-ray images and real-time dynamic images of finger bending. The researchers see great scope for further improvements by exploring other types of lead-free perovskites and perovskite derivatives.