New multinuclear europium(III) complexes as phosphors applied in fabrication of near UV-based light-emitting diodes

Two new multinuclear europium(III) complexes, [Eu(AFTFBD)3]2(1,4-bmb) and [Eu(AFTFBD)3]3(tmb) were designed and synthesized, where HAFTFBD was 2-acetylfluorene-4,4,4-trifluorobutane-1,3-dione, 1,4-bmb was 1,4-bis[2-(2′-pyridyl)benzimidazolyl]benzene and tmb was 1,3,5-tris[2-(2′-pyridyl)benzimidazolyl]benzene. The complexes were characterized by IR, UV–visible, photoluminescence (PL) spectroscopy and thermogravimetric analysis (TGA). The complexes emit the characteristic red luminescence of Eu3+ ion due to the 5D0–7FJ (J = 0–4) transitions under 395 nm-light excitation. Bright red light-emitting diodes were fabricated by coating the selected complex (Eu(AFTFBD)3)3(tmb) onto ∼395 nm-emitting InGaN chips, and the LEDs show appropriate CIE chromaticity coordinates in red area. All these results suggest that the Eu(III) complexes are promising candidates as red component for application in fabrication of near UV-based white light-emitting diodes.