Color-Variable Light-Emitting Diode Utilizing Conducting Polymer Containing Fluorescent Dye

A color-variable light-emitting diode has been realized utilizing conducting polymer, poly(2,5-dioctyloxy-p-phenylene vinylene) (ROPPV-8), mixed with fluorescent dye, 8-hydroxyquinoline aluminum (Alq3). The electroluminescence of the diode changes from orange to greenish-yellow in color with increasing applied voltage. On the other hand, a light-emitting diode with the two-layer structure of ROPPV-8 and Alq3 shows only light emission from the ROPPV-8 layer. This difference is discussed in terms of the carrier injection process to Alq3.