Structure and luminescence properties of green-emitting NaBaScSi2O7:Eu2+ phosphors for near-UV-pumped light emitting diodes

Abstract

Green-emitting phosphor Eu²⁺ doped NaBaScSi₂O₇ was synthesized by a solid-state reaction, and the photoluminescence properties were investigated in conjunction with a structural analysis. The crystallographic occupancy of Eu²⁺ in the Sc silicate NaBaScSi₂O₇ matrix was studied based on the Rietveld refinements results and the crystal chemistry rules. The optimum concentration of Eu²⁺ in the NaBaScSi₂O₇ phosphor was about 10 mol%, and the concentration quenching mechanism was verified to be the dipole–dipole interaction. Upon excitation at 365 nm, the composition-optimized NaBaScSi₂O₇:Eu²⁺ exhibited strong green light peaking at 501 nm with the CIE chromaticity (0.0706, 0.5540) and a high internal quantum efficiency of about 65%. The thermally stable luminescence properties were also studied and compared with those of the commercial green phosphors. A white light emitting diode (w-LED) lamp was finally fabricated by using the present green phosphor and the commercial blue and red phosphors, which exhibited a high color rendering index (R_a) of 86.5 at a correlated color temperature of 2528 K with CIE coordinates of x = 0.353, y = 0.324. These results suggest that NaBaScSi₂O₇:Eu²⁺ is a potential green phosphor candidate for near-UV-pumped w-LEDs.