New blue electroluminescent n-type polyfluorene copolymers with a 1,3,4-oxadiazole unit in the main chain

Abstract

Novel polyfluorene copolymers alternately having an 1,3,4-oxadiazole unit in the main chain were prepared by both one-step and two-step methods for polyoxadiazole synthesis. They displayed highly efficient blue photoluminescence, the properties of which were affected by the extent of conjugation and the changes in the electron density by a side chain. An electrochemical analysis of the polymers using cyclic voltammetry suggested that they could be used as electron-transport/hole-blocking materials as well as blue emission materials for polymer light-emitting diodes. A simple double-layer device consisting of poly(N-vinylcarbazole) as a hole-transport layer and poly [(9,9'-didodecylfluorene-2,7-diyl)-alt-((1,4-bis(1,3,4-oxadiazole)-2,5-di(2-ethylhexyloxy)phenylene)-5,5'-diyl)] as an emission layer exhibited narrow blue electroluminescence with a maximum at 430 nm. (C) 2004 Wiley Periodicals, Inc.