A bright and moisture-resistant red-emitting Lu3Al5O12:Mn4+,Mg2+ garnet phosphor for high-quality phosphor-converted white LEDs

Abstract

The rational and delicate synthesis of Mn⁴⁺ activated red-emitting oxide phosphors with high photoluminescence quantum yield (PLQY) and photo-stability for developing high-quality w-LEDs still remains a great challenge. Herein, we demonstrate a simultaneous ion co-substitution design strategy to synthesize a red-emitting Lu₃Al₅O₁₂:Mn⁴⁺,Mg²⁺ garnet phosphor delicately with the assistance of MgF₂. The Mn⁴⁺ activated garnet phosphor exhibits superior moisture resistance properties and high PLQY (ca. 72.41%), which emits a bright and narrow-band red light peaking at ∼670 nm due to the ²E–⁴A₂ spin-forbidden transition of Mn⁴⁺ upon UV excitation. Remarkably, MgF₂ as a charge compensator & flux can not only accelerate the solid state reaction, but also greatly improve the emission intensity. Furthermore, by employing the as-prepared Lu₃Al₅O₁₂:Mn⁴⁺,Mg²⁺ as a red component, we fabricate a warm w-LED with a high color rendering index (R_a = 81.4) and low color temperature (CCT = 4766 K) based on a UV chip and commercial blue and yellow phosphors.