Diphenylethyne based β-diketonate europium(III) complexes as red phosphors applied in LED

Two new CF3-substituted β-diketonates, prepared through Sonogashira coupling reaction and Claisen condensation reaction, were used to synthesize the corresponding antenna europium(III) ternary complexes using 1,10-phenanthroline as an ancillary ligand. These two complexes exhibit a good thermal stability from thermogravimetric analysis. Photophysical properties such as FT-IR spectra, UV–Vis absorption spectra, excitation and emission spectra, luminescence decay curves and quantum yields based on the complexes were investigated and compared. Significantly, quantum yield (0.29) of the 4-F substituted complex is approximately seven times higher than that (0.04) of the unsubstituted one, which indicates the 4-F substituted β-diketonates ligand is a better candidate for sensitizing Eu3+ ion luminescence. Both complexes show the highest excitation intensity around 395 nm, which is perfectly matched with the emission spectrum of commercial ∼395 nm-emitting InGaN chips. A bright red light-emitting diode (LED) with an efficiency of 2.64 lm/W was fabricated by coating the 4-F substituted complex onto a ∼395 nm-emitting InGaN chip. The emission around 395 nm from the InGaN chip was completely absorbed in the spectrum of the LEDs. Its CIE chromaticity coordinates (x = 0.6616, y = 0.3251) based on the emission spectrum are close to the National Television Standard Committee (NTSC) standard value for red color. All the results indicate that the 4-F substituted complex is a promising candidate as red components in fabrication of white light-emitting diode (WLED) with a high color-rendering index.