Novel Mn4+ doped red phosphors composed of MgAl2O4 and CaAl12O19 phases for light-emitting diodes

Abstract

Red emitters based on CaAl₁₂O₁₉:Mn⁴⁺ have been attracting extensive attention due to their advantages of being rare-earth-free and chemically stable. However, their relatively low luminescence efficiencies will seriously hinder their application in light-emitting diodes (LEDs). In this regard, the promising red phosphors of CaAl₁₂O₁₉:Mn⁴⁺ were synthesized with enhanced luminous efficiency by introducing the coexisting phase of MgAl₂O₄. Importantly, an approximately 5 times enhancement of integrated intensity in the emission spectrum was observed for the phosphor with the coexisting phase compared to that with a single phase. Their crystal structures, morphologies and photoluminescence properties and the mechanism of improved luminescence were systematically investigated. Upon exciting them by using near-ultraviolet or blue LEDs, an efficient red emission was achieved with a maximum peak at ∼658 nm. In order to evaluate their potential application, a warm white LED and a plant growth LED were fabricated by using the prepared phosphors in combination with YAG:Ce³⁺ and InGaN-based blue chips.