Thermally Stable Red-Emitting Ca₁₈K₃Sc(PO₄)₁₄:Mn²⁺ Phosphor and Enhanced Luminescence by Energy Transfer Between Ce³⁺-Eu²⁺-Mn²

It is significant and valuable to investigate novel and high-performance red-emitting phosphors for high-quality wLED applications. Based on this consideration, we developed a novel Mn²⁺-doped red Ca₁₈K₃Sc(PO₄)₁₄:Mn²⁺ (CKSP:Mn²⁺) phosphor. The emission peak of CKSP:Mn²⁺ is located at 640 nm, presenting a broadband red emission with a fwhm of 79 nm under 405 nm excitation. The CKSP:1.0Mn²⁺ phosphor shows superior thermal stability. At 150 °C, the integrated PL intensity and peak intensity of the CKSP:1.0Mn²⁺ phosphor maintain 93.2 and 85.7% of those at 25 °C, respectively. Through the strategy of energy transfer among Ce³⁺-Eu²⁺-Mn²⁺, the PL intensity of Mn²⁺ has increased by nearly 118 times, and the quantum yield has improved from 6 up to 72%. The structure-related photoluminescence and energy transfer mechanisms are discussed in detail. The as-fabricated wLED pumped by a 370 nm LED chip combining commercial the green (Sr,Ba)₂SiO₄:Eu²⁺ phosphor, blue BaMgAl₁₀O₁₇:Eu²⁺ phosphor, and the as-synthesized CKSP:1.0Mn²⁺, 0.02Eu²⁺, 0.40Ce³⁺ phosphor shows excellent color quality (CCT = 5555 K, Ra = 87), which indicates that the CKSP:1.0Mn²⁺, 0.02Eu²⁺, 0.40Ce³⁺ phosphor has extraordinary broad prospects in future wLED applications.