Growth and luminescence properties of pure, Ce-doped and Eu-doped LiSr₂I₅ single crystals

In this work, pure, Ce³⁺-doped, and Eu²⁺-doped LiSr₂I₅ single crystals were grown, and the effects of ion doping on their luminescence properties were investigated. Single crystals with diameters of 10 and 15 mm were grown using the vertical Bridgman method. The optical band gap of LiSr₂I₅ was 4.84 eV, which was higher than the theoretically calculated band gap. The luminescence spectrum revealed an emission peak at 420 nm characteristic of STE luminescence, consistent with the radiative emission spectrum. Time-resolved fluorescence decay spectroscopy under 375 nm excitation of the pure LiSr₂I₅ crystal exhibited both a short-lived component of 72 ns and a long-lived component of 200 ns. The exciton lifetimes for the Ce³⁺-doped and Eu²⁺-doped crystals were 244 ns and 366 ns, respectively. Temperature-dependent spectroscopy revealed that doping with Eu increased the exciton binding energy and enhanced exciton stability in STE luminescence. Overall, LiSr₂I₅ exhibits low toxicity and high radioluminescence intensity, thus laying good foundations for potential application in low-dose radiography.