Cs₂WCl₆ Nanocrystals as Near-Infrared Scintillator Material for X-ray Detection

The near-infrared (NIR) luminescent scintillators are integrated into high quantum efficiency silicon-based photodetectors, making them a promising solution for highly efficient radiation detection applications. Halide perovskites are promising scintillator materials due to their excellent X-ray absorption capacity. However, it remains challenging to realize efficient NIR-emitting scintillators in these materials. Fortunately, Cs2WCl6 vacancy-ordered double perovskites have shown great potential as an NIR scintillator due to their efficient NIR emission. The currently common synthesis methods for Cs2WCl6 require a longer period or involve impurity phases, making the process less efficient and yielding products of lower purity. In this study, we report an improved coprecipitation method that can easily prepare Cs2WCl6 double perovskite, offering a more efficient and facile process. The composition, morphology, and phase of prepared Cs2WCl6 are characterized by energy dispersive spectroscopy (EDS), field emission scanning electron microscopy (FESEM), and X-ray diffraction (XRD), confirming the acquisition of pure-phase perovskite materials. In terms of luminescence, Cs2WCl6 shows a broadband and asymmetric emission from 800 to 1250 nm with a large Stokes shift (∼560 nm). Combined with a long excited-state lifetime of 7.34 μs, the intense NIR emission in Cs2WCl6 is considered to originate from self-trapped excitons (STEs). Temperature-dependent PL spectra demonstrate strong electron–phonon coupling, which induces significant lattice distortion in order to produce STEs. Importantly, Cs2WCl6 nanocrystal films exhibit strong NIR radioluminescence under X-ray irradiation. These results may stimulate research into the potential application of Cs2WCl6 as a prototype for high spatial resolution X-ray imaging.