Broadly tunable full-visible-spectrum ZnS/ZnO:Mn²⁺ composite microphosphor for warm WLED applications

Phosphor development for warm white LEDs (w-WLEDs) is key to enhancing light quality, energy efficiency, stability, and environmental sustainability. Mn²⁺-doped phosphors, known for their broad visible emission, are especially promising for UV-pumped w-WLEDs. While halide and garnet systems show potential, they suffer from toxicity and complex synthesis, making ZnO and ZnS attractive, stable alternatives. In this study, tunable full-visible-spectrum ZnS/ZnO:Mn²⁺ phosphors were synthesized via a simple thermal diffusion method. Structural analyses (XRD, Raman) revealed temperature-driven phase evolution, while PL and PLE measurements confirmed strong UV absorption and broad 400-700 nm emission from both host and Mn²⁺ centers. Emission was effectively tuned by Mn²⁺ concentration, with the ZnS/ZnO:0.1% Mn²⁺ sample emitting warm white light (CIE: x = 0.35, y = 0.37; CCT: 4920 K; decay time: 0.35 ms; activation energy: 0.31 eV). A phosphor-coated LED prototype demonstrated high luminous efficacy (127.7 lm per W), CIE coordinates (x, y) = (0.4974, 0.3405), CRI of 72, and a correlated color temperature (CCT) of 2506 K, suitable for warm lighting applications.