Improving phosphorescence of Sr₂MgSi₂O₇: Eu²⁺ phosphor by Tm³⁺ co-doping for AC-LEDs

Phosphors with afterglow can be used as phosphor-convertors in AC-LEDs to reduce the scintillation because the phosphorescence compensates for decayed emission in milliseconds. To improve the phosphorescent intensity, Tm³⁺ was employed as a co-dopant in Sr₂MgSi₂O₇: Eu²⁺ phosphors. Compared to the long afterglow induced by Dy³⁺ co-doping, a suitable concentration of Tm³⁺ increased the number of excited electrons of Eu²⁺ by an energy transfer process so that fluorescent intensity was improved. After switching off the excitation, the accumulated excited electrons accompanied by the de-trapped electrons from the oxygen vacancies led to an improved phosphorescence intensity of the Eu²⁺. The Sr₂MgSi₂O₇: Eu²⁺, Tm³⁺ synthesized in this study is a promising candidate for phosphor-conversion in AC-LEDs.