A highly luminescent dinuclear Eu(III) complex based on 4,4′-bis (4″,4″,4″-trifluoro-1″,3″-dioxobutyl)-o-terphenyl for light-emitting diodes

A dinuclear Eu(III) complex Eu2(btbt)3·4H2O·CH3CH2OH·N(CH2CH3)3 was synthesized, where H2(btbt) was 4,4′-bis (4″,4″,4″,-trifluoro-1″,3″-dioxobutyl)-o-terphenyl. The composition and structure of the complex were characterized by elemental analysis, IR, UV–vis and FAB-MS spectroscopy. The complex emits the characteristic red luminescence of Eu3+ ion due to the 5D0 → 7FJ (J = 0–4) transitions under ∼395 nm-light excitation with good luminescent quantum efficiency (32%) and exhibits high thermal stability (337 °C). Bright red light-emitting diodes (LEDs) were fabricated by coating the complex onto a ∼395 nm-emitting InGaN chip. When the mass ratio of the red phosphor to the silicone is 1:30, the efficiency of the fabricated LEDs with the europium complex is 0.98 lm w−1. The CIE chromaticity coordinates of the LEDs are x = 0.6057 and y = 0.3137, which are close to the National Television Standard Committee (NTSC) standard values for red color. The results indicate that the complex may act as a red component in the fabrication of near UV InGaN-based white light-emitting diodes with high color-rendering index.