Designing Metal Halides for Fast Neutron Imaging Scintillators: Lessons from Perovskite Nanocrystals and Ionic Liquids

The lead halide perovskites have captivated the research community due to their exceptional optoelectronic properties that enable high performance as solar cells and light emitters. In particular, perovskite nanocrystals (NCs) have demonstrated their potential as next-generation light emitters, with applications ranging from QLED displays to X-ray scintillators. Recent work on metal halides for fast (high-energy, &gt;1 MeV) neutron detection has shown that they have the potential to deliver low-cost, efficient scintillators for this application, with the advantages of high spatial resolution, low gamma-ray sensitivity, and negligible afterglow on the timescale of seconds. However, there are several challenges to overcome before these materials can displace the commercial polypropylene screens (embedded with microscale ZnS:Cu phosphors).<br/> This presentation will summarize three studies in this field, which have each contributed design rules that will enable a more complete understanding of how to design metal halides for this application. A first comparison of perovskite nanocrystals with a variety of other halide and chalcogenide NCs showed that FAPbBr₃ NCs offered the highest light yield, while CsPbBrCl₂:Mn²⁺ NCs offered the highest spatial resolution. Composition and thickness-dependent measurements highlighted the need to 1) enhance concentration and 2) reduce self-absorption for all NC systems. Subsequently, we sought to further test these design rules by 1) exploring the use of metal halide ionic liquids for maximal concentration, and 2) separately pursing the optimized synthesis and doping in CsPb(Br_xCl_1–x)₃:Mn²⁺ NCs to improve concentration and eliminate reabsorption.<br/>These follow-up studies showcased the importance of these design principles for improved fast neutron scintillation, as the latter system demonstrated the capacity for concentrations above 100 mg/mL while essentially eliminating self-absorption, while the former system yielded significantly higher spatial resolution and competitive light yields. This presentation will synthesize this series of results into a succinct summary of the needs of this lesser-known application, providing the fundamental background to engage with the burgeoning field of fast neutron imaging and design the perovskite materials that can deliver the next generation of fast neutron scintillators.