MULTICOLOR ELECTROLUMINESCENCE DIODES USING OLIGOPHENYLENE AND OLIGOPHENYLENEVINYLENE MULTILAYERS

We present electroluminescence (EL) characteristics for single-layer a nd multilayer thin films with oligophenylenevinylenes and oligophenyle nes. Light-emitting diodes (LEDs) were fabricated by vacuum evaporatio n techniques of both the oligomer films and the negative electrodes. D epending on the substrate temperature, highly ordered or polycrystalli ne layers were obtained. Our LEDs emit blue light in the range of 425- 460 nm (oligophenylenes) and in a broad visible range of 400-600 nm (o ligophenylene/oligophenylenevinylene multilayers). The current-voltage (I-V) characteristics of our devices show rectifying behaviour with h igh rectification ratios. We report I-V characteristics and the respec tive threshold voltages, quantum efficiencies, photoluminescence (PL), EL and optical absorbance of the thin films and the devices.