Design and WLED application of KAlSiO4:Eu2+, Mn2+ phosphors with high quantum efficiency and high color stability prepared by a refiring strategy
Among the green-cyan phosphors widely used in white LEDs, the full width at half maximum, thermal stability and quantum efficiency are key performance indicators. This kind of phosphor should have stable peak shape and peak position when working at different temperatures. It should simultaneously exhibit ultrawideband emission, which is conducive to the realization of two-color white light and simplification of the preparation process of white LED devices. In this paper, a series of KAlSiO 4 :Eu 2+ , Mn 2+ luminescent materials were synthesized by a high-temperature recalcination strategy. Phase analysis and refinement results showed that the samples were effectively synthesized. After the first calcination, a bright green powder was obtained. The main emission peak was at 514 nm, and the FWHM was 30 nm. After recalcination, the color of the light emission from the representative samples changed from green to cyan-green, which was very close to white light, under near-UV irradiation. The emission range was wide, including blue and green light, and the full width at half maximum could reach 150 nm. After recalcination, the emission intensity of the representative samples increased by 3.4 times, and the quantum efficiency reached 90 % under near-UV excitation. The emission intensity at 150 °C was 82 % of that at room temperature. The Raman spectra showed that recalcination had a good effect on the lattice symmetry of the samples and promoted their luminescence intensity. The experimental value of the optical bandgap of the matrix was 5.6 eV, whereas the DFT-calculated bandgap was 4.8 eV, indicating good thermal stability. The chromaticity shift of the sample at high temperatures was very small, indicating good chromaticity stability. A commercial broadband red powder and representative samples after refiring were combined with 365 nm near-UV chips. The color rendering index of the white LED devices exhibited under different driving currents was greater than 90, indicating that the refiring strategy successfully improved the luminous performance of the representative samples. KAlSiO 4 :Eu 2+ , Mn 2+ phosphors were verified to have good application prospects in the field of white LED lighting. This work provides a new idea and technology for calcination and color control of luminescent phosphors.
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