Highly Efficient Color-Tunable OLED Based on Poly(9,9-dioctylfluorene) Doped with a Novel Europium Complex

Tunable dichromic electroluminescence is obtained from a blend of Eu3+ complex in polyfluorene by a single spin-coatable emitting layer device with external quantum efficiency as high as 1%, the highest reported in literature to our knowledge. The design of a complex whose ligand increases the site isolation of EU3+ ion allows reduction of the back-transfer quenching effects that prevented up to now the multicolor electroluminescence of EU3+ complex/polyfluorene blends. Energy transfer mechanisms involving singlet and triplet excitons are analyzed by focusing on the effects of site isolation and polarity of the new ligand that provide homogeneous dispersion of the complex in the conjugated polymer.