Green Eu 2+-doped Ba 3Si 6O 12N 2 phosphor for white light-emitting diodes: Synthesis, characterization and theoretical simulation

Abstract

The Eu 2+-doped Ba 3Si 6O 12N 2 green phosphor (Eu x Ba 3− x Si 6O 12N 2) was synthesized by a conventional solid state reaction method. It could be efficiently excited by UV-blue light (250–470 nm) and shows a single intense broadband emission (480–580 nm). The phosphor has a concentration quenching effect at x=0.20 and a systematic red-shift in emission wavelength with increasing Eu 2+ concentration. High quantum efficiency and suitable excitation range make it match well with the emission of near-UV LEDs or blue LEDs. First-principles calculations indicate that Ba 3Si 6O 12N 2:Eu 2+ phosphor exhibits a direct band gap, and low band energy dispersion, leading to a high luminescence intensity. The origin of the experimental absorption peaks is clearly identified based on the analysis of the density of states (DOS) and absorption spectra. The photoluminescence properties are related to the transition between 4f levels of Eu and 5d levels of both Eu and Ba atoms. The 5d energy level of Ba plays an important role in the photoluminescence of Ba 3Si 6O 12N 2:Eu 2+ phosphor. The high quantum efficiency and long-wavelength excitation are mainly attributed to the existence of Ba atoms. Our results give a new explanation of photoluminescence properties and could direct future designation of novel phosphors for white light LED.