Multicolour electroluminescence diodes using oligophenylene and oligophenylenevinylene multilayers

We present electroluminescence (EL) characteristics for single-layer and multilayer thin films with oligophenylenevinylenes and oligophenylenes. Light-emitting diodes (LEDs) were fabricated by vacuum evaporation techniques of both the oligomer films and the negative electrodes. Depending on the substrate temperature, highly ordered or polycrystalline 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 (oligophenylene/oligophenylenevinylene multilayers). The current-voltage (I-V) characteristics of our devices show rectifying behaviour with high rectification ratios. We report I-V characteristics and the respective threshold voltages, quantum efficiencies, photoluminescence (PL), EL and optical absorbance of the thin films and the devices.