Simultaneous enhancement of red luminescence and thermal stability of a novel red phosphor: A Li+-Eu3+ co-occupied site strategy in BaAl2Ge2O8 lattices

The rapid development of phosphor-converted white light emitting diodes (pc-WLEDs) requires new red phosphors with efficient and thermally stable luminescence for high-quality warm-white lighting. However, it is still a challenge to discover red phosphors with facile synthesis, high internal quantum efficiency (IQE), excellent thermal stability and high color purity. Herein, a novel red-emitting Eu3+ activated barium dialuminum digermanate (BaAl2Ge2O8, BAGO) phosphor showing strong red emission at 610 nm was prepared. The IQE is improved from 32.91% to 78.84% by employing a charge compensation strategy. The lithium-ion co-doped BAGO:Eu3+ phosphor exhibits a nearly twofold increase in integral photoluminescence (PL) intensity and the high color purity reaches 94.17%. Impressively, the PL intensity of the BAGO:Eu3+,Li+ phosphor drops by only 2.6% at 150 °C of that at room temperature. Finally, the pc-WLED using the red BAGO:Eu3+,Li+ phosphor exhibits white light with the chromaticity coordinate of (0.3515, 0.3495), a high color-rendering index of 92 and a low correlated color temperature of 4746 K. All these results manifest that BAGO:Eu3+,Li+ phosphor is a suitable red phosphor for near-ultraviolet (NUV) chip-based pc-WLEDs.