ABSTRACT Low‐dimensional metal halides, especially Cu‐based systems, have emerged as promising x‐ray scintillators due to high scintillation efficiency. However, mitigating non‐radiative energy losses remains a critical hurdle to achieving further performance gains. In this work, efficient exciton utilization was achieved in Bridgman‐grown Cs 3 Cu 2 I 5 single crystals by introducing Mn 2 + to modulate exciton relaxation dynamics. The synergistic effect of efficient Mn 2+ ‐centered emission and the energy transfer from STE to Mn 2 + and Mn 2+ ‐Mn 2+ pairs effectively suppresses non‐radiative dissipation, achieving a remarkable light yield of 120 000 photons MeV −1 under x‐ray irradiation. Thanks to ultrabright scintillation yield, the Cs 3 Cu 2 I 5 :Mn single crystals demonstrate a superior spatial resolution of 30 lp mm −1 and a low detection threshold of 91 nGy s −1 , enabling clear resolution of fine features in a 50 µm copper grid. This study clarifies the exciton‐dopant interactions in Mn 2+ ‐activated Cs 3 Cu 2 I 5 scintillators and provides guidance for designing efficient materials for x‐ray imaging.
Gao et al. (Sun,) studied this question.