LIGHT-EMITTING-DIODES BASED ON PHENYLENEVINYLENE OLIGOMERS WITH DEFINED CHAIN LENGTHS

We present characteristic electroluminescence data on single-layer dev ices based on three different oligo phenylenevinylene compounds with d efined chain lengths. Light-emitting diodes (LEDs) were prepared by su bsequent vacuum evaporation of the oligomer him and the Al top electro de onto an indium-tin oxide (ITO) substrate. The LEDs show Light emiss ion in the spectral range of yellow to orange depending on the conjuga tion length of the compound used. We report photoluminescence and opti cal absorption data of the thin sublimed films, together with the wave length dependence of the electroluminescence and with the current-volt age characteristics of the LED devices. The redox behavior and, thus, the pertinent electronic energy levels of the phenylenevinylene oligom ers were characterized using cyclic voltammetry. The experimental data can be interpreted within a consistent model description. (C) 1997 El sevier Science S.A.