Lu3+ doping induced photoluminescence enhancement in novel high-efficiency Ba3Eu(BO3)3 red phosphors for near-UV-excited warm-white LEDs

Abstract

Ba₃Eu(BO₃)₃ (BEB) and Lu³⁺ doped BEB red phosphors were successfully synthesized by a high-temperature solid-state reaction method. X-ray diffraction (XRD) patterns, excitation and emission spectra, decay lifetimes, CIE coordinates, internal quantum efficiency, and thermal stability of these phosphors were systematically studied. Under 395 nm excitation, these phosphors exhibited high-brightness red emissions centred at 611 nm. In addition, it was found that doping appropriate amounts of Lu³⁺ ions into BEB phosphors can improve their photoluminescence intensity and internal quantum efficiency. The integrated emission intensity of BEB:0.3Lu³⁺ phosphor was about 1.34 times that of BEB phosphor. Compared with commercial red phosphor Y₂O₂S:Eu³⁺, BEB:0.3Lu³⁺ phosphor showed better color purity (91.4%) and higher emission intensity (about 3.25 times). Surprisingly, the BEB:0.3Lu³⁺ phosphor had a high internal quantum efficiency of almost 87%, which was higher than that of 83% for BEB phosphors. Meanwhile, the BEB:0.3Lu³⁺ phosphors also exhibited good thermal stability with activation energy around 0.14 eV, and the integrated emission intensity at 423 K remained about 52% of that at 303 K. Finally, by using commercial BaMgAl₁₀O₁₇:Eu²⁺ blue phosphors, commercial (Ba,Sr)₂SiO₄:Eu²⁺ green phosphors, as-prepared BEB:0.3Lu³⁺ red phosphors and a 395 nm near-ultraviolet-emitting light-emitting diode (LED) chip, a prototype warm white LED device was fabricated, which showed good color rendering index (CRI = 84.7) and low correlated color temperature (CCT = 3377 K).