Lead halide perovskites have recently shown great potential as X-ray scintillators; however, the toxicity of the lead element seriously restricts their applications. Herein we report a new lead-free and self-absorption-free scintillator based on Rb 2 CuCl 3 metal halide. The Rb 2 CuCl 3 exhibits a near-unity photoluminescence quantum yield (99.4%) as well as a long photoluminescence lifetime (11.3 μs). Furthermore, Rb 2 CuCl 3 demonstrates an appreciable light yield of 16 600 photons per megaelectronvolt and a large scintillation response with a linear range from 48.6 nGy air s −1 to 15.7 μGy air s −1 . Notably, the detection limit is as low as 88.5 nGy air s −1 , enabling a reduced radiation dose to the human body when a medical and security check is conducted. In addition, Rb 2 CuCl 3 exhibits good stability against the atmosphere, continuous ultraviolet light, as well as X-ray irradiation. The combination of the decent scintillation performance, low toxicity and good stability suggests the Rb 2 CuCl 3 could be a possible promising X-ray scintillator.

An all-inorganic lead-free halides Cs−Cu−I system, represented by Cs 3 Cu 2 I 5 and CsCu 2 I 3 , has attracted attention for their good photophysical characteristics recently. Successive works had reported their application potential in light-emitting devices. However, there is no report for CsCu 2 I 3 in X-ray scintillation detectors so far. We notice that CsCu 2 I 3 may be advantageous in such an application due to the one-dimensional crystal structure, the congruent-melting feature, and the high spectral matching to some photosensors. In this work, we explore the scintillation properties and imaging application of CsCu 2 I 3 in X-ray scintillator detector. The oriented structure is designed to enhance the imaging performance of a CsCu 2 I 3 detector. Close-space sublimation process and nanoscale seed screening strategy are employed to realize this design by producing a large-area (25 cm 2 ) CsCu 2 I 3 thick film layer with the oriented nanorod structure. This CsCu 2 I 3 detector eventually achieves a high spatial resolution of 7.5 lp mm −1 in X-ray imaging.

Flat panel displays enjoy 100 billion‐dollar markets with significant penetration in daily life, which require efficient, color‐saturated blue, green, and red light‐emitting diodes (LEDs). The recently emerged halide perovskites have demonstrated low‐cost and outstanding performance for potential LED applications. However, the performance of blue perovskite LEDs (PeLEDs) lags far behind red and green cousins, particularly for color coordinates approaching (0.131, 0.046) that fulfill the Rec. 2020 specification for blue emitters. Here, a high‐efficiency, lead‐free perovskite, CsEuBr3, is reported that exhibits bright blue exciton emission centered at 448 nm with a color coordinates of (0.15, 0.04), contributed from Eu‐5d→Eu‐4f/Br‐4p transition with an optical band gap of 2.85 eV. Further optical characterizations reveal its short excited‐state lifetime of 151 ns, excellent exciton diffusion diffusivity of 0.0227 cm2 s−1, and high quantum yield of ≈69%. Inspired by these findings, deep‐blue PeLEDs based on all‐vacuum processing methods, which have been demonstrated as the most successful approach for the organic LED industry, are constructed. The devices show a maximum external quantum efficiency of 6.5% with an operating half‐lifetime of 50 mins at an initial brightness of 15.9 cd m−2. It is anticipated that this work will inspire further research on lanthanide‐based perovskites for next‐generation LED applications.