A novel deep red emission phosphor BaAl2Ge2O8:Mn4+ for plant growth LEDs

Abstract

The luminescence properties of BaAl2Ge2O8:Mn4+ are investigated in this paper. The excitation spectrum of BaAl2Ge2O8:Mn4+ shows two broad bands. The absorption band centred at 288 nm is attributed to the overlap of the Mn4+-O2− charge transfer transition and the 4A2 → 4T1 transition of the Mn4+ ions. The weak absorption band centred at 435 nm is attributed to the 4A2 → 4T2 transition of the Mn4+ ions. The luminescence spectrum shows two emission peaks at 652 nm and 668 nm due to the 2E → 4A2 transition of the Mn4+ ions. As the concentration of the Mn4+ ions increases, the lifetime of the phosphor decreases from 1.766 ms to 1.595 ms. The chromaticity coordinates are (0.720, 0.279), which is a deep red emission. The luminescence of BaAl2Ge2O8:Mn4+ contributes to plant growth and can be applied to plant illumination sources.