Achieving a Record Scintillation Performance by Micro‐Doping a Heterovalent Magnetic Ion in Cs ₃ Cu ₂ I ₅ Single‐Crystal

Abstract An ultrabright, ultrafast, and low‐cost ideal scintillator has been critically absent and is sorely desired in scintillation detection, but has hitherto not been found. Here, a high‐quality bulk Cs ₃ Cu ₂ I ₅ :Mn single‐crystal scintillator with ultrahigh light yield (≈95 772 photons per MeV, ¹³⁷ Cs γ‐rays), excellent energy resolution (3.79%, 662 keV), and ultrafast scintillation decay time (3 ns, 81.5%) is reported. In mechanism, it is found that micro‐doping of a heterovalent magnetic ion (at the ppm level) can effectively modulate the luminescence kinetics of self‐trapped excitons in the scintillator. Compared with previous reports, the introduction of trace amounts of magnetic Mn ²⁺ (≈18.6 ppm) in Cs ₃ Cu ₂ I ₅ single‐crystal shortens the scintillation decay time by several hundred times, transforming the slow decay into an ultrafast decay. Simultaneously, the light yield is also increased about three times to the highest value so far. From the comprehensive performance of the micro‐doped Cs ₃ Cu ₂ I ₅ :Mn single‐crystal, these excellent scintillation properties, physical characteristics suitable for practical applications, and low‐cost advantages render this single‐crystal an ideal scintillator with great potential for commercialization.