BLUE ELECTROLUMINESCENCE FROM A PROCESSABLE DERIVATIVE OF PPV BASED COPOLYMER WITH TRI(ETHYLENE OXIDE) SIGMENTS IN THE BACKBONE

Abstract

A new light-emitting copolymer [poly(distyrylbenzene-block-tri(ethylene oxide)) (DSB-TEO)], containing alternating rigid, conjugated distyrylbenzene as light-emitting units and flexible tri(ethylene oxide) as ionic conductive units, was synthesized via Wittig reaction. The polymer has fairly good solubility in chloroform and excellent film-forming ability. Single-layer and double-layer light-emitting diodes with indium tin oxide anodes and calcium cathodes were fabricated, and the photoluminescence (PL) and electroluminescence (EL) properties were investigated. Single layer light emitting diode with DSB-TEO as the active layer(ITO/PEDOT:PSS/DSB-TEO/Ca) showed bright blue emission with luminance over 450 cd/m 2 and efficiency of 0.1 cd/A. Inserting a thin layer of Alq3 between the copolymer and the cathode improved the device performance, luminance over 1000 cd/m 2 and efficiency of 0.5 cd/A could be achieved. The enhanced emission in the longer wave part due to Alq 3 contribution is negligible. This polymer may also be a good candidate material for light emitting electrochemical cells (LECs).