Wenbo Ma

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 Cs 2 Ag 0.6 Na 0.4 In 1-y Bi y Cl 6 . By controlling the content of the heavy atom Bi 3+ , 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 CsPbBr 3 (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 μGy air , and dynamic X-ray imaging of finger bending without a ghosting effect was demonstrated under a low-dose rate of 47.2 μGy air 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.

Abstract Environmental friendly metal halides have become emerging candidates as energy downconverting emitters for lighting and X‐ray imaging applications. Herein, luminescent single crystals of tetramethylammonium manganese chloride (C 4 H 12 NMnCl 3 ) and tetraethylammonium bromide ((C 8 H 20 N) 2 MnBr 4 ) are synthesized via a facile room‐temperature evaporation method. C 4 H 12 NMnCl 3 and (C 8 H 20 N) 2 MnBr 4 with octahedrally and tetrahedrally coordinated Mn 2+ have correspondingly exhibited red and green emission peaking at 635 and 515 nm both originating from 4 T 1 – 6 A 1 transition of Mn 2+ with high photoluminescence quantum yield (PLQY) of 91.8% and 85.1% benefiting from their specific crystal structures. Thanks to their strong photoexcitation under blue light, high PLQY, tunable emission spectra, good environmental stability, the white light‐emitting diode based on blending of C 4 H 12 NMnCl 3 and (C 8 H 20 N) 2 MnBr 4 delivers an outstanding luminous efficacy of 96 lm W −1 , approaching commercial level, and shows no obvious photoluminescence intensity degradation after 3000 h under operation. In addition, manganese halides also demonstrate interesting characteristics under X‐ray excitation, C 4 H 12 NMnCl 3 and (C 8 H 20 N) 2 MnBr 4 exhibit steady‐state X‐ray light yields of 50 500 and 24 400 photons MeV −1 , low detectable limits of 36.9 and 24.2 nGy air s −1 , good radiation hardness, and X‐ray imaging demonstration with high‐resolution of 5 lp mm −1 . This work presents a new avenue for luminescent Mn‐based metal halides toward multifunctional light‐emitting applications.

also enjoys facile solution synthesis with large scalability, excellent repeatability, and low cost.