Electrophosphorescent Polyfluorenes Containing Osmium Complexes in the Conjugated Backbone

Electrophosphorescent copolymers have been synthesized by covalent bonding of a red‐emitting osmium complex Os(bpftz), which contains two 3‐trifluoromethyl‐5‐(4‐tert‐butyl‐2‐pyridyl)triazolate (bpftz) cyclometalated ligands, into the backbone of a bipolar polyfluorene (PF) copolymer. Employing these copolymers, a highly efficient red polymer light‐emitting diode has been realised that has an external quantum efficiency of 18.0%, a maximum brightness of 38 000 cd m−2, and an emission centered at 618 nm. In addition, after incorporating appropriate amounts of green‐emitting benzothiadiazole (BT) and the aforementioned Os(bpftz) into the bipolar PF, an efficient white‐light electroluminescent polymer is obtained that displays simultaneous blue, green, and red emissions. Highly efficient red‐electrophosphorescent devices have been realised by incorporating Os complexes into the conjugated backbone of a blue polyfluorene copolymer that contains both hole‐and electron‐transporting pendent groups. The best device performance is a maximum external quantum efficiency of 18.0% with a peak brightness of 38 000 cd m−2.