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 (Lu0.99Tm0.01)2O3 and (Lu0.84In0.15Tm0.01)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 (Lu0.99Tm0.01)2O3 phosphor presented abnormal thermal quenching effect.