Energy transfer from self-trapped excitons to rare earth ions in Cs2ZrCl6 perovskite variants

Abstract

Rare earth ion doping in metal halides has been a promising method for imparting and tailoring their optical and optoelectronic performances towards versatile optical applications. In this work, the relationships among intrinsic self-trapped excitons (STEs), sub-band gap defects and rare earth ions Tb³⁺ in Cs₂ZrCl₆:Tb³⁺ perovskite variants were established. Cs₂ZrCl₆ exhibits dual emission, deriving from the intrinsic STEs and sub-band gap defects owing to the Zr⁴⁺ or Cl⁻ vacancies, respectively. Doping Tb³⁺ facilitated the characteristic emission (⁵D₄–⁷F_J=6,5,4,3) of Tb³⁺ ions and the energy transfer from STEs to Tb³⁺ ions. Moreover, the participation of defect states and thermally activated delayed fluorescence (TADF) might lead to a high concentration of STEs, which in turn causes the abnormal thermal quenching effect. These findings not only provide a more in-depth understanding of the luminescence properties of Cs₂ZrCl₆, but also provide a new direction towards achieving tunable emission colors based on the energy transfer from STEs to rare earth ions.