An Efficient Narrow-band Blue-emitting Phosphor Ba₃Y₂B₆O₁₅:Bi³⁺ and Its Application

Abstract

At present, the development of efficient (high quantum efficiency and high thermal stability) narrow-band emitting phosphors is a crucial problem in the application of white light emitting diodes (WLED) for high-performance liquid crystal display (LCD) backlights. In this work, an efficient narrow-band blue emitting phosphor Ba3Y2B6O15:Bi 3+ was prepared by high temperature solid state method, and its structure and properties were characterized and calculated. By using the density functional theory (DFT), Ba3Y2B6O15 is calculated to be a direct band gap material with a high band gap value of 4.67 eV, which is a necessary condition for achieving high quantum efficiency phosphors. The experiment results show that Ba3Y2B6O15:0.5%Bi 3+ has a narrow-band blue-emitting spectrum with a full width at half maximum (FWHM) of 2168 cm −1 (36.2 nm) at 409 nm, which is owing to the 3 P1→ 1 S0 transition of Bi 3+ ions. The emission spectra of Ba3Y2B6O15:0.5%Bi 3+ can be split into two peaks at 406 and 422 nm, respectively, because there are two kinds of Y ions (Y1 and Y2) in the crystal cell of Ba3Y2B6O15. Under the 365 nm UV radiation, the Ba3Y2B6O15:0.5%Bi 3+ exhibits high internal quantum efficiency (IQE＝93.8%), and ultra-high color purity (98.9%). The high quantum efficiency and narrow-band emission spectrum are mainly due to the compact and highly symmetric crystal structure of Ba3Y2B6O15 matrix. The photoluminescence (PL) intensity of Ba3Y2B6O15:0.5%Bi 3+ remains 73.9% of the initial intensity at 150 ℃, and there is almost no color drift. The thermal quenching activation energy (Ea) of Ba3Y2B6O15:0.5%Bi 3+ was calculated to be 0.290 eV by the Arrhenius Equation, which indicates that Ba3Y2B6O15:0.5%Bi 3+ has high thermal stability. When Y 3+ is partially substituted by Sc 3+ , the emission spectrum of Ba3ScxY2-xB6O15:Bi 3+ (0 ≤ x ≤ 1.6) is redshifted with the increase of x. Finally, the blue phosphor Ba3Y2B6O15:0.5%Bi 3+ was mixed with commecial green and red phosphors and then coated them on a 365 nm chip to fabricate a WLED device. Under a driven current of 20 mA, the correlated color temperature of the obtained WLED is 5679 K and the color gamut can reach 95.3% NTSC. Above results indicate that Ba3Y2B6O15:Bi 3+ is a promising phosphor for high-performance LCD backlights. Keywords highly-efficient phosphor; narrow-band emitting; blue phosphor; Ba3Y2B6O15:Bi 3+