A thienylene-phenylene copolymer with di(ethylene oxide) side chains and its use in light emitting diodes

A thienylene-dialkoxyphenylene copolymer was prepared by condensation between a bis-stannylthiophene reagent and a substituted dibromobenzene derivative in the presence of a palladium catalyst. Owing to the presence of 2-(2-butoxy-ethoxy)-ethoxy polar side chains the polymer was soluble in most organic solvents and exhibited excellent glass adhesion properties. It allowed the formation of homogeneous thin films on indium tin oxide (ITO) by spin coating. The electrochemical and optical properties of thin films of the material have been studied. The calculated band gap derived from cyclic voltammetry data (2.21 eV) is in good agreement with the one calculated from the UV-VIS spectrum edge ( 2.15 eV). A single layer light emitting diode (LED) was fabricated in the configuration of ITO/polymer/ AI. Electroluminescent maximum was recorded at 600 nm corresponding to a red orange emission. The diode exhibited an operating voltage at ca. 5 V and a high current rectification ratio (3 x 10(3)). (C) 2002 Elsevier Science B.V All rights reserved.