Exciton-harvesting enabled efficient charged particle detection in zero-dimensional halides.

Materials for radiation detection are critically important and urgently demanded in diverse fields, starting from fundamental scientific research to medical diagnostics, homeland security, and environmental monitoring. Low-dimensional halides (LDHs) exhibiting efficient self-trapped exciton (STE) emission with high photoluminescence quantum yield (PLQY) have recently shown a great potential as scintillators. However, an overlooked issue of exciton-exciton interaction in LDHs under ionizing radiation hinders the broadening of its radiation detection applications. Here, we demonstrate an exceptional enhancement of exciton-harvesting efficiency in zero-dimensional (0D) Cs₃Cu₂I₅:Tl halide single crystals by forming strongly localized Tl-bound excitons. Because of the suppression of non-radiative exciton-exciton interaction, an excellent α/β pulse-shape-discrimination (PSD) figure-of-merit (FoM) factor of 2.64, a superior rejection ratio of 10^-9, and a high scintillation yield of 26 000 photons MeV^-1 under 5.49 MeV α-ray are achieved in Cs₃Cu₂I₅:Tl single crystals, outperforming the commercial ZnS:Ag/PVT composites for charged particle detection applications. Furthermore, a radiation detector prototype based on Cs₃Cu₂I₅:Tl single crystal demonstrates the capability of identifying radioactive ²²⁰Rn gas for environmental radiation monitoring applications. We believe that the exciton-harvesting strategy proposed here can greatly boost the applications of LDHs materials.