Acid Post-Treatment Triggered High-Efficiency Blue-Emitting LiNa₂Sr₈B₁₂O₂₄F₆Cl:Eu²⁺ Phosphors toward Multipurpose LED Applications

To facilitate the industrial application of phosphor-converted white-light-emitting diodes (pc-WLEDs), it is crucial to overcome the significant challenge of creating high-efficiency, thermally stable blue phosphors. Exploiting the extensive band gap and discrete anionic groups in the compound LiNa2Sr8B12O24F6Cl, a groundbreaking blue-emitting phosphor designated as a-LNSBOFC:Eu2+ (acid-treated LiNa2Sr8B12O24F6Cl:Eu2+) has been developed. This phosphor was synthesized through a meticulous solid-state reaction followed by an acid post-treatment process, setting a new benchmark in the field. Moreover, the acid post-treatment process can remove the impurities and surface defects from the phosphor, resulting in simultaneous enhancements in both luminescence intensity (approximately 1.4 times) and quantum efficiency (79% → 90%). The a-LNSBOFC:Eu2+ blue phosphor demonstrates remarkable thermal stability, retaining 89% efficiency at 150 °C, and maintains superior chromaticity (Δx = 0.0039, Δy = 0.0075) within the temperature range of 25–150 °C, with color consistency varying minimally between 2.2 × 10–3 and 1.7 × 10–2. Its ability to resist thermal quenching predominantly originates from the substantial 5.67 eV band gap of the host matrix, which efficiently curtails thermal ionization. Crucially, prototype WLED devices employing this blue phosphor produce high-quality warm white light (CCT = 3958 K and Ra = 90) and achieve 72% of the NTSC color space according to the CIE 1931 standards. This advancement heralds a promising direction for the development of efficient and thermally robust blue phosphors tailored to LED technologies. The a-LNSBOFC:Eu2+ phosphor reported here shows great foreground and potentiality to be a next-generation blue emitter for near-ultraviolet excited high-quality warm white WLEDs and backlights in liquid-crystal display technology.