Whether Cs3Cu2I5 crystal is a fast-decaying scintillator?

The zero-dimensional perovskite Cs₃Cu₂I₅ crystal has been widely investigated as a novel high performance scintillator in recent years. However, there is an obvious contradiction on the scintillation decay time (microsecond-scale vs. nanosecond-scale) in different reports, which causes confusion on the intrinsic properties of the crystal as well as its application potentials. In order to dispel the confusion, Cs₃Cu₂I₅ single crystals were grown by both the vertical Bridgman and aqueous solution methods and their scintillation properties were investigated and compared. Despite differences in crystal quality, all samples grown by both methods exhibit a dominant slow-decaying component with an average decay time of about 880 ns, without significant difference in the timing property. This result is consistent with most of the previous reports, indicating that Cs₃Cu₂I₅ crystal is more probably a slow-decaying scintillator, contrary to recent claims of fast-decaying behavior. The slow decaying characteristic is also consistent with its self-trapped excitons (STE) luminescence mechanism.