Two-color emitting of Eu2+ and Tb3+ co-doped Sr2MgSi2O7 for UV LEDs

• An efficient nonradiative energy transfer from Eu2+ to Tb3+ occurs.
• The optimal concentration of Tb3+ and Eu2+ ions are about 17.5 mol% and 1.5 mol%, respectively.
• The CIE color coordinates change from a blue to greenish blue region as Tb3+ concentration increasing.
• The bluish green phosphor SMSO: Eu2+, Tb3+, Na+ has high chromaticity stability.

An intense bluish green phosphor, Sr2MgSi2O7: Eu2+, Tb3+, was synthesized by high temperature solid-state reaction. The photoluminescence excitation and emission spectra, the lifetime, concentration effect and the temperature-dependent properties are investigated in detail. The results show that an efficient nonradiative energy transfer from Eu2+ to Tb3+ occurs. Tb3+ ions give an intense green emitting light by a strong excitation band of Eu2+ ions at 350–430 nm, matching well with the dominant emission band of (n)-UV (350∼420 nm) LEDs. These results demonstrate that Tb3+ ion with low 4f–4f absorption efficiency in (n)-UV region can play a role of activator in narrow green emitting phosphor potentially useful in (n)-UV GaN-based LED through efficient energy feeding by allowed 4f–5d absorption of Eu2+ with high oscillator strength.