Light-emitting electrochemical cells and light-emitting diodes based on ionic conductive poly(phenylene vinylene): a new chemical sensor system

Red-orange light-emitting electrochemical cells (LECs) based on poly[1,4-(2 ,5-bis(1,4,7,10-tetraoxaundecyl))phenylene vinylene] also named poly[2,5-bi s(triethoxy-methoxy)-1,4-phenylene vinylene], (BTEM-PPV) are fabricated and characterized. BTEM-PPV combines good electronic conductivity with ionic c onductivity in the oxidized and reduced state due to its conjugated backbon e and oligo(ethylene oxide) attached as side chains. When applying this pol ymer in LECs one obtains devices of moderate brightness and with fast respo nse times. This high performance is achieved without blending an additional ionic conductive polymer into the film. The response time of such devices driven with square waveform voltage pulses was determined to be 480 mu s. T he turn-on voltage for electroluminescence occurs at 2 V and at 3 V a brigh tness of about 35 cd/m(2) was obtained. Due to the covalent linkage of glym e like side chains to the PPV backbone, BTEM-PPV, complexed with metal ions , shows an ionochromic effect in the absorption spectra and also in the ele ctroluminescence spectra, which can be a new approach to chemical sensors. (C) 1999 Published by Elsevier Science S.A. All rights reserved.