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

Area of Science:

• Materials Science
• Solid-State Chemistry
• Optoelectronics

Background:

• Development of warm white LEDs (w-WLEDs) is crucial for improving light quality, energy efficiency, and sustainability.
• Manganese-doped (Mn²⁺) phosphors offer broad visible emission suitable for UV-pumped w-WLEDs.
• Existing halide and garnet phosphors face challenges with toxicity and complex synthesis, necessitating stable alternatives like ZnO and ZnS.

Purpose of the Study:

• To synthesize tunable full-visible-spectrum ZnS/ZnO:Mn²⁺ phosphors using a simple thermal diffusion method.
• To investigate the structural and photoluminescent properties of the synthesized phosphors.
• To evaluate the performance of a phosphor-coated LED prototype for warm lighting applications.

Main Methods:

• Synthesis of ZnS/ZnO:Mn²⁺ phosphors via thermal diffusion.
• Structural characterization using X-ray Diffraction (XRD) and Raman spectroscopy.
• Photoluminescence (PL) and Photoluminescence Excitation (PLE) measurements to analyze emission and absorption properties.
• Fabrication and testing of a phosphor-coated LED prototype.

Main Results:

• Temperature-driven phase evolution was observed in the ZnS/ZnO:Mn²⁺ phosphors.
• Strong UV absorption and broad emission spanning 400-700 nm were confirmed.
• Emission color was tuned by adjusting Mn²⁺ concentration, with optimal warm white light achieved at 0.1% Mn²⁺.
• The LED prototype showed high luminous efficacy (127.7 lm/W), a CRI of 72, and a CCT of 2506 K.

Conclusions:

• ZnS/ZnO:Mn²⁺ phosphors synthesized via thermal diffusion are effective for producing warm white light.
• The developed phosphors offer tunable emission and good performance characteristics for w-WLEDs.
• This approach provides a stable, non-toxic, and efficient alternative for lighting applications.