A novel fluorinated europium ternary complex for highly efficient pure red electroluminescence

A novel fluorine-functionalized europium(III) ternary complex, i.e., Eu(DBM)3(BFPP), in which DBM was dibenzoylmethane and BFPP 2, 3-bis(4-fluorophenyl)pyrazino[2,3-f] [1,10]phenanthroline, was designed, synthesized and characterized. The complex emits the characteristic red emission of trivalent europium ion due to the 5D0 → 7Fj (j = 0–4) transitions under photo excitation with good luminescent quantum efficiency (0.55) and exhibits high thermal stability (387 °C). The organic light-emitting diodes (OLEDs) employing the complex as a dopant emitter with the structures of ITO/TPD (40 nm)/CBP:Eu-complex (30 nm)/Bphen (10 nm)/Alq3 (20 nm)/LiF (1 nm)/Al (150 nm) were successfully fabricated. The 4 wt.% Eu(DBM)3(BFPP) doped device exhibited the maximum luminance of 1766 cd/m2 and a peak current efficiency of 4.6 cd/A, corresponding to the high external quantum efficiency of 2.27%.