A europium(III) organic ternary complex applied in fabrication of near UV-based white light-emitting diodes

A beta-diketone, 2-acetylfluorene-4,4,4-trifluorobutane-1,3-dione (HAFTFBD), and its three europium(III) complexes, Eu(AFTFBD)(3)a <...2H(2)O, Eu(AFTFBD)(3)(TPPO)(2) and Eu(AFTFBD)(3)phen, were designed and synthesized, where TPPO was triphenylphosphine oxide and phen was 1,10-phenanthroline. The complexes were characterized by IR, UV-visible, photoluminescence (PL) spectroscopy and thermogravimetric analysis (TGA). The results show that the Eu(III) complexes exhibit a high thermal stability,and wide and strong excitation bands when monitored at 613 nm. Excited by similar to 395 nm near UV light, the complexes emitted strong and characteristic red light due to f-f transitions of the central Eu3+ ion, and no emission from the ligands was found. The photoluminescence mechanism of the europium(III) complexes was investigated and proposed as a ligand-sensitized luminescence process. Among the three europium(III) complexes, Eu(AFTFBD)(3)phen exhibits the highest thermal stability and the most excellent photoluminescence properties. A bright red light-emitting diode was fabricated by coating the Eu(AFTFBD)(3)phen complex onto an similar to 395 nm-emitting InGaN chip, and the LED showed appropriate CIE chromaticity coordinates (x=0.66, y=0.33). A white LED with CIE chromaticity coordinates (x=0.32, y=0.32) was prepared with Eu(AFTFBD)(3)phen as red phosphor, indicating that Eu(AFTFBD)(3)phen can be applied as a red component for fabrication of near ultraviolet-based white light-emitting diodes.