Optimized photoluminescence of K₂SiF₆:Mn⁴⁺ phosphors for LED solid-state lighting

Red-emitting K₂SiF₆:Mn⁴⁺ phosphors were synthesized by using the redox reaction in aqueous solutions mixed with SiO₂, KMnO₄, HF, and H₂O₂. The photoluminescence (PL) spectrum of the as-synthesized K₂SiF₆:Mn⁴⁺ phosphors showed a narrow emission band with 5 peaks in the wavelength range from 610 to 650 nm. The main peak at 630 nm had a narrow full width at half maximum (FWHM) (<10 nm). The emission intensity of the K₂SiF₆:Mn⁴⁺ phosphor ex'd at 460 nm was about 2.5 times higher than that of the phosphor excited at 365 nm. The K₂SiF₆:Mn⁴⁺ samples synthesized with a ratio of SiO₂:KMnO₄ = 0.2:1 exhibited the best luminescence intensity. The K₂TiF₆:Mn⁴⁺ phosphors were synthesized by using the cation exchange method in order to compare its luminescent properties with those of the K₂SiF₆:Mn⁴⁺ phosphors, and the luminescent intensity of the K₂SiF₆:Mn⁴⁺ phosphors was about 1.5 times higher than that of the K₂TiF₆:Mn⁴⁺ phosphors. Thus, the K2SiF6:Mn4+ phosphors may be considered to be efficient red-emitting phosphors for blue-emitting GaN light-emitting diodes.