Nonradiative centers in Ba3Si6O12N2:Eu2+ phosphors observed by the below-gap excitation method

• We fabricated high quantum efficiency Eu2+-doped Ba3Si6O12N2 green phosphors.
• We used the two-wavelength excited PL (TWEPL) method to detect NRR centers.
• TWEPL: a below-gap excitation light is superposed on an above-gap excitation light.
• PL intensity will change when the BGE energy matches optical transitions via NRR.
• We detected a distribution of NRR centers in BSON phosphors for the first time.

By a conventional solid state reaction method in air and N2/H2 atmosphere, we successfully made two Eu2+-doped Ba3Si6O12N2 (BSON) green phosphors to characterize their nonradiative recombination (NRR) processes. They showed a broad excitation spectrum from 250 to 450 nm which could be efficiently excited by UV or blue LED, and produced an intense broadband emission from 460 to 620 nm. We have clarified a distribution of NRR centers by superposing a below-gap excitation (BGE) light on an above-gap excitation (AGE) light and observing an increase of photoluminescence (PL) intensity. Different BGE effect of two samples implies that the synthesis condition influences the defects in BSON phosphors. Due to the coexistence of the NRR center and trap centers, we obtained a unique behavior of the PL intensity increase as a function of the AGE density.