ELECTROLUMINESCENCE AND PHOTOLUMINESCENCE INVESTIGATIONS OF THE YELLOW EMISSION OF DEVICES BASED ON LADDER-TYPE OLIGO(PARA-PHENYLENE)S

We report investigations of electroluminescence and photoluminescence in several soluble ladder-type oligo(para-phenylene)s which we have used in a range of single- and double-layer electroluminescence devices. In double-layer devices which incorporate a thin film of poly(phenylenevinylene) (PPV) as a hole transport layer, yellow emission with 0.6% internal quantum efficiency can be achieved. We find that pure blue emission can be obtained by diluting the luminescent polymer into a poly(9-vinylene carbazole) (PVK) matrix. This gives a blue-emitting electroluminescent device with more than 0.1% internal quantum efficiency.