Removal of deep traps in Lu2O3:Tm phosphors via formation of continuous solid solutions with In2O3 enabling widely tailorable bandgap energy

Abstract

Bandgap engineering has been effectively used to reduce the shallow-trap defects (e.g. antisite defects), but there are still rare reports on the removal of deep-trap defects (e.g. oxygen defects). In this work, our proposed strategy of In³⁺ substitution for Lu³⁺ via the formation of continuous (Lu,In)₂O₃ solid solutions can be used to widely tailored the bandgap energy. These solid solutions prepared from the chemical co-precipitation route presented the rounded morphology and their particle sizes increased at a higher In³⁺ content. The (Lu,In)₂O₃:Tm phosphor powders exhibited characteristic Tm³⁺ emissions arising from its intra‐4f¹² multi‐transitions upon UV excitation into strong broad charge transfer bands. The luminescence intensity reached the highest level at 15 at.% In³⁺ concentration. The In³⁺ incorporation was found to red-shift the charge transfer bands and shortened the florescence lifetimes. The luminescence quenching was dominated by exchange interaction while the theoretical and experimental quenching concentration of Tm³⁺ coincided well with each other (both ∼1 at.%). The trap depth in the In³⁺ free Lu₂O₃:Tm phosphor was determined to be ∼0.61 eV and these electron traps could be almost fully buried at the In³⁺ concentration above 5 at.%. Both the (Lu_0.99Tm_0.01)₂O₃ and (Lu_0.84In_0.15Tm_0.01)₂O₃ phosphors exhibited good thermal stability with high thermal-quenching activation energies (∼0.45 eV for the former and ∼0.39 eV for the latter). However, the (Lu_0.99Tm_0.01)₂O₃ phosphor presented abnormal thermal quenching effect.