Scintillation Properties and Electronic Structure of Intrinsic and Extrinsic Mixed Elpasolites Cs2NaRBr3I3 (R = La, Y)

TL;DR

This study investigates the scintillation mechanisms and electronic structures of mixed-anion elpasolite halides Cs2NaRBr3I3 (R = La, Y), revealing their high light yield and tunable properties for improved radiation detection applications.

Contribution

It provides experimental and theoretical insights into the scintillation mechanisms of mixed-elpasolites, highlighting their potential for high-performance radiation detectors.

Findings

High light yield from self-trapped exciton emission (20,000-40,000 ph/MeV)

Ce doping introduces additional Ce3+ emission pathways

Electronic structure calculations confirm strong STE stability and high binding energies

Abstract

Scintillators attract wide research interest for their distinct applications in radiation detection. Elpasolite halides are among the most promising scintillators due to their high structural symmetry and good scintillation performance. Better understanding of their underlying scintillation mechanism opens up new possibilities in scintillator development. In this work, we employ a variety of experimental techniques to study the two mixed-anion elpasolites Cs2NaRBr3I3 (R = La, Y). The emission of intrinsic Cs2NaRBr3I3 with a light yield ranging from 20,000 to 40,000 ph/MeV is dominant by self-trapped exciton emission. Partial substitution of R with Ce introduces a competing emission, the Ce3+ 5d to 4f radiative transition. Ab initio calculations were performed to investigate the electronic structures as well as the binding energies of polarons in Cs2NaRBr6. The calculated large self-trapped exciton binding energies are consistent with the observed high light yield due to self-trapped exciton emission. The unique electronic structure of halide elpasolites as calculated enhances the STE stability and the STE emission. The highly tunable scintillation properties of mixed-anion elpasolites underscore the role of their complex scintillation mechanism. Our study provides guidance for the design of new elpasolites scintillators with exceptional energy resolution and light yield desirable for applications.