Alcohol-soluble conjugated poly(fluorene-co-thiophene) as an electron-transport material for polymer light-emitting diodes.

A series of alternating polyfluorene copolymers containing fluorene (P1-OF), bithiophene (P2-BT), and thiophene (P3-TH) moieties have been synthesized via a palladium-catalyzed Suzuki coupling reaction. Among them, theP3-THpolymer highly contains hydroxyl groups which provides enough solubility in polar solvents such as alcohols and dimethylformamide. Multilayer polymer light-emitting diodes have been fabricated using a semiconducting polymer, F8BT, as an emissive layer and the methanol-solubleP3-THas an electron-transport layer. By the device configuration of ITO/PEDOT/TFB/F8BT/P3-TH/LiF/Al, it shows a luminescence efficiency of 1.48 cd/A and a turn-on voltage of 4.6 V. The emission with maxima at 448 nm and 495 nm which fell in the blue region with the CIE coordinates (x = 0.18, y = 0.24). [ABSTRACT FROM PUBLISHER]