Synthesis and properties of a novel red electroluminescent conjugated polymer containg naphthothiadiazole

A series of aminoalkyl-substituted polyfluorene copolymers with 4, 7-dithien-2-yl-2, 1, 3-naphtho-thiadiazole (SNS) with different contents were synthesized by Suzuki coupling reaction. The polymers are soluble in organic solvent, such as chloroform, toluene. All the polymers emit red light (more than 700 nm) under UV excitation in the solid state. It was found that the PFN-SNS polymers show a good device performance when high work-function metals, such as Al, are used as the electron-injection cathode replacing conventional low work-function cathodes such as Ca and Ba. The maximum external quantum efficiency is more than 1.3% with Al as cathode.