Novel high-brightness yellow light-emitting phosphor Ba2GdGaO5: Bi3+ for NUV-pumped WLED application

Abstract

Developing high-brightness luminescence materials is always a significant work, especially for bismuth-based phosphors, due to their incompletely spin-allowed intra-ionic electron transition of 1S0–3P1. In this work, high-brightness light emitting of Bi3+ ion was achieved in Ba2GdGaO5, and its internal quantum efficiency (IQE) reaches up to 96%. Under the near-ultraviolet (NUV) light excitation, Bi3+-activated Ba2GdGaO5 emits a broad-band yellow light peaked at 566 nm with full width at half maximum (FWHM) of 126 nm. Compared with commercial yellow phosphor Y3Al5O12: Ce3+, the as-prepared sample shows a similar emission band, but preforms a better thermal stability. The significant photoluminescence characteristic of Bi3+ ion in Ba2GdGaO5 is demonstrated to be derived from the extra-ionic electronic transition of Bi3+ ion, which is identified as metal to metal charge transfer band (MMCT). This mechanism was discussed in detailed combined with the crystal and electronic structure of Ba2GdGaO5, which is expected to pave an effective way for developing high-brightness bismuth-based phosphors.