Developing Thermally Stable Defect-Assisted Phosphors of BaSc₂Ge₃O₁₀:Bi³⁺ for Pc-UV-LEDs Applications

Current ultraviolet (UV) light sources are dominated by blacklights that contain mercury vapor. Improper disposal or accidental breakage of these lamps can lead to serious pollution. Phosphor-converted light-emitting diodes (pc-UV-LEDs) have the potential to replace these mercury-containing lamps, making them more environmentally friendly. To improve the adjustability of the UV emission and reduce production cost, a series of UV-emitting phosphors were developed by introducing Bi³⁺ in BaSc₂Ge₃O₁₀ (BSGO) which has a broad bandgap of 5.88 eV. The phosphor exhibits a negative thermal quenching effect that results from thermally activated defects. Despite this, the emission intensity of the phosphor sustains up to 107% at 353 K and 93% at 473 K compared to the intensity at 298 K. The internal quantum efficiency and the external quantum efficiency reach 81.0 and 49.32%, respectively, under 305 nm excitation. A pc-UV-LEDs were fabricated by combining the phosphor with a chip. The resulting device emits a broad band ranging from 295 nm to 450 nm, covering part of the UVB (280 nm ∼ 315 nm) and UVA (315-400 nm) regions. Our work has the potential to promote the replacement of current blacklights, including high-pressure mercury lamps and fluorescent low-pressure mercury lamps, by pc-UV-LEDs in applications such as bug zappers and tanning beds. Moreover, the phosphor exhibits desirable long persistent luminescence, which extends its prospect of applications.