Dual color tuning in Ce3+-doped oxyfluoride ceramic phosphor plate for white LED application

Ceramic phosphor plates of cerium (Ce3+)-doped oxyfluoride were fabricated by the solid-state reaction method. These phosphors exhibit efficient emission, with the novel feature of color tuning by varying both the doping concentration and excitation wavelength. As the Ce3+ concentration increases, the excitation spectrum broadens by a factor of 1.6, and the excitation peak wavelength shifts from 390 to 435nm, and there is a variation in excitation energy of similar to 10%. Luminescence spectrum of low Ce3+ concentration samples is tuned from blue to green with the change of excitation wavelength. The emission peak exhibits a shift of 58nm into the red spectral region, varying the Ce3+ concentration from 0.05 to 0.1mol%; whereas this shift is only 6nm when Ce3+ content changes from 0.25 to 1mol%. Photoluminescence (PL) quantum yield has achieved 76%. The crystal structure was examined using X-ray diffraction to explain its possible influence on the redshift luminescence. A proof of concept of white LED was constructed using a 450nm blue LED chip with an oxyfluoride phosphor plate, showing a luminous efficacy (LE) of 64lm/W with a color rendering index of 74.