Improved luminescence and afterglow emission from Mn2+/Si4+ co-doped AlN by combustion synthesis method

Highlights: • A Mn²⁺/Si⁴⁺ co-doped strategy was used to improve both luminescence and afterglow properties of the orange-red AlN phosphor by combustion synthesis. • The mechanisms behind this promotion were discussed in detail. • A more reasonable identification of the excitation spectral term of AlN:Mn²⁺ is proposed. • The effect of Si⁴⁺ on the morphology of as-synthesized AlN:Mn²⁺ phosphors was observed. -- Abstract: An orange-red emitting Mn²⁺/Si⁴⁺ co-doped AlN phosphor was prepared by an efficient combustion synthesis method. Phase identification and structure characterization were performed using powder X-ray diffraction (XRD) and refined by the Rietveld method. Luminescence and afterglow properties of the AlN-based phosphors such as photoluminescence spectra (PL), CIE values, afterglow decay curves, thermoluminescence glow curves (TL) were systematically studied. Using the Tanabe-Sugano diagram, the Racah parameters B, C, and crystal field splitting parameter Dq of as-prepared phosphor were calculated to be 812 cm⁻¹, 2168 cm⁻¹, and 780 cm⁻¹, respectively. The luminescence intensity and afterglow time were increased, respectively, by about 1.1 and 2.2 times after 3% Si⁴⁺ co-doping. Particular attention was paid to study the mechanism of Si⁴⁺ co-doping on improving luminescence properties using a combination of the above-mentioned method and X-ray photoelectron spectroscope (XPS). Two hypothetical stress cancellation and charge rebalance effects due to Si⁴⁺ co-doping were discussed. Besides, it was found a shallower trap level (0.56 eV, compared to 0.84 eV for those without Si⁴⁺ co-doping) was formed after the co-doping of Si⁴⁺, which results in enhanced afterglow performance.