MMCT-induced high-bright yellow light-emitting phosphor Bi3+-activated Ba2YGaO5 used for WLED

Based on the wide application of Bi3+-activated phosphors in Near-ultraviolet light-emitting diode (NUV-LED) chips for inducing healthy lighting, it is necessary to reveal the characteristics of high-quality Bi3+-activated phosphors. In this study, a high bright yellow light is realized with Bi3+-activated Ba2YGaO5, showing an Internal quantum efficiency (IQE) of up to 92%. Under 350 nm excitation, Ba2YGaO5: Bi3+ emits a broad yellow light peak at 587 nm with full width at half maximum (FWHM) of 135 nm, while simultaneously exhibiting good thermal stability; these results are superior to those of the commercial yellow phosphor Y3Al5O12: Ce3+. Moreover, significant cathodoluminescence properties are observed with Ba2YGaO5: Bi3+. These excellent luminescence properties are demonstrated to result from the D-level state described as the Metal-to-metal charge transfer (MMCT) state. Combined with the crystal and electronic structure of Ba2YGaO5, the origin of the D-level state along with its luminous mechanism is investigated in detail in this work, which may pave the way for developing more high-quality Bi3+-activated phosphors for use in NUV-LED chip-induced healthy lighting.