Study on structure and optical property of highly symmetric Ba3Y2B6O15: Bi/Tb/Eu/Lu phosphor and its application in wLEDs

Borate-based phosphors, as a critical class of luminescent materials, have garnered significant attention due to their stable crystal structures, wide bandgaps, excellent thermal stability, and robust spectral tunability, making them essential components in white light-emitting diodes ( w LEDs) technologies. In this work, a high-symmetry Ba 3 Y 2 B 6 O 15 (BYB) phosphor co-doped with Bi 3+ , Tb 3+ , Eu 3+ , and Lu 3+ was synthesized via a multi-step sol-gel method. Different photoluminescence (PL) behaviors of Bi 3+ , Tb 3+ and Eu 3+ in BYB were systematically revealed. By modulating the PL spectrum via energy transfer (ET) from Bi → Tb → Eu, ‘cool’ white-light emission was achieved. A strategy of replacing Y 3+ with Lu 3+ was adopted to adjust the crystal field splitting and symmetry. This modification broadens the blue light coverage range in Bi 3+ PL, increases the hypersensitive transition of Eu 3+ ( 5 D 0 → 7 F 2 ), increase the intensity of red emission. They achieved their optimal balance ultimately. The improved structural compactness and rigidity reduced electron-phonon coupling effects, endowing the phosphor with superior chemical/thermal stability. Finally, a high-performance phosphor-converted w LED (pc- w LED) device with chromaticity coordinates of (0.361, 0.358), a luminous efficacy (LE) of 95.2 lm/W, was fabricated by integrating the optimized BYB: Bi/Tb/Eu/Lu phosphor with a UV LED chip using remote ‘cap’ packaging, demonstrating exceptional performance.