Enhanced exciton luminescence and fast scintillation potential in Sr2+-activated CsPbCl3 single crystals

Abstract

Single crystals of pristine and Sr²⁺-activated CsPbCl₃ were grown using the vertical Stockbarger technique, and their luminescence properties were investigated. Under excitation with synchrotron-radiation photons of 7.75 eV, which substantially exceeds the band gap energy, the pristine crystals exhibit a pronounced excitonic emission band with a maximum at ∼417 nm, whereas Sr²⁺-activated crystals reveal the emergence of additional exciton-like bands in the near edge region, accompanied by a tendency of the edge emission to shift toward higher energies. The activated crystals also demonstrate a pronounced enhancement of luminescence intensity, reaching nearly a tenfold increase for CsPbCl₃:Sr (1 mol%). The additional exciton-like emission band Sr²⁺-activated crystals may originate from excitons localized at defect-related sites. The average decay time constants of the excitonic emission bands in both the pristine and the activated crystals are approximately 500 ps at 10 K and 60 ps at 77 K. The temperature evolution of luminescence intensity is interpreted in terms of electron escape beyond the Onsager sphere, whose radius decreases with increasing temperature, whereas the temperature-induced changes in the decay time constants are attributed to thermally assisted exciton dissociation. The pronounced enhancement of near band edge luminescence intensity in Sr²⁺-activated CsPbCl₃ crystals highlights their potential for application as fast scintillators.