Light Management of Metal Halide Scintillators for High‐Resolution X‐Ray Imaging

The ever‐growing need to inspect matter with hyperfine structures requires a revolution in current scintillation detectors, and the innovation of scintillators is revived with luminescent metal halides entering the scene. Notably, for any scintillator, two fundamental issues arise: Which kind of material is suitable and in what form should the material exist? The answer to the former question involves the sequence of certain atoms into specific crystal structures that facilitate the conversion of X‐ray into light, whereas the answer to the latter involves assembling these crystallites into particular material forms that can guide light propagation toward its corresponding pixel detector. Despite their equal importance, efforts are overwhelmingly devoted to improving the X‐ray‐to‐light conversion, while the material‐form‐associated light propagation, which determines the optical signal collected for X‐ray imaging, is largely overlooked. This perspective critically correlates the reported spatial resolution with the light‐propagation behavior in each form of metal halides, combing the designing rules for their future development. This perspective considers light propagation in metal halide scintillators as the focus. By correlating the reported spatial resolution with light propagation in various forms, this perspective clarifies and deepens the understanding of untouched yet fundamental issues, namely, material‐form‐associated light propagation in metal halide scintillators, and provides the design rules for their future development.