Crystal Structure-Guided Design of a Single-Site Blue Phosphor BaHf(BO3)2:Eu2+ with High Color Purity for WLEDs

Near-ultraviolet (n-UV) chip-excited white light-emitting diodes (WLEDs) offer a promising strategy to overcome the blue-light hazard and poor color quality inherent in conventional white-light sources. However, the lack of high-performance blue-emitting phosphors remains a critical bottleneck. Herein, we report a novel Eu2+-activated borate blue phosphor, BaHf(BO3)2/Eu2+, prepared by a high-temperature solid-state reaction. When excited at 330 nm, the Eu2+ ions occupied in the six-coordinated metal site of BaHf(BO3)2 produce bright blue emission, with a full-width at half-maximum of ∼27 nm, CIE coordinates of (0.1670, 0.0100), and a high color purity of 99.36%. Concentration quenching analysis reveals an optimal Eu2+ doping level of 0.06, beyond which dipole−dipole interaction causes luminescence quenching. By combining BaHf(BO3)2/Eu2+ with commercial green and red phosphors on a 365 nm n-UV chip, a WLED device is achieved with a high color rendering index of 90.1 and a warm correlated color temperature of 3003 K. These findings reveal that this phosphor holds promise as a blue-emitting candidate for high-quality, health-friendly WLED lighting.