Ultrafast Scintillator Based on Zirconium‐Doped Cesium Zinc Chloride Single Crystals and Their Charge Carrier Dynamics

Scintillators have been widely used for high‐energy radiation imaging. It is in great demand and challenge to develop scintillator materials with fast decay time, high scintillation light yield, and low detection limit for high‐resolution imaging applications such as time‐of‐flight positron emission tomography. However, it is still a challenge to develop the ultrafast carrier dynamics to achieve 100% ultrafast decay time with high scintillation light yield. To meet the demand, a series of component‐tunable Cs2ZnCl4: x%Zr single crystals as promising ultrafast scintillators is successfully developed. With 8% of Zr‐dopant (Cs2ZnCl4: 8%Zr), the single crystal exhibits high light yield (28000 photons MeV−1) and low detection limit (51 nGy s−1) under X‐ray excitation. Photo‐induced transient absorption signals on sub‐nanosecond and nanosecond scales ensure almost 100% fast decay time (≈3 ns) in nanoseconds under γ‐ray excitation. In particular, the different radiative transition processes are achieved under ultraviolet and high‐energy radiation due to the tunable carrier dynamics from the shallow trapped state to the self‐trapped exciton (STE) state. The Cs2ZnCl4: x%Zr single crystals contribute to effective high energy radiation absorption, as a result Cs2ZnCl4: x%Zr single crystals feature high light yield (28000 photons MeV−1), low detection limit (51 nGy s−1), and almost 100% fast decay time (≈3.5 ns). For a totally new finding, the UV and high‐energy radiation‐induced charge carriers show completely different dynamics.