ELECTROLUMINESCENCE OF ORGANIC THIN-FILMS BASED ON BLENDS OF POLYSTYRENE AND FLUORESCENT DYES

Blue and red light-emitting diodes were constructed as devices in whic h a polystyrene/dye blend was sandwiched between a calcium electrode a nd a transparent indium-tin oxide electrode. As dye molecules, four al koxy-substituted derivatives of 2,5-dialkoxy-1,4-bis(2-phenylvinyl)ben zene (i.e. p-phenylene vinylene oligomers), a derivative of bisanthrac ene 3'-tetrachloro-9,9'-dimethoxy-10,10'-bianthracene) and the laser d ye e-2-methyl-6-(p-dimethylaminophenylvinyl)-4H-pyran (DCM) were used. The critical field for light emission in devices using 20 wt.% PPV ol igomers in polystyrene was found to be of the order of 2 x 10(8) V m-1 . The dependence of the device conductivity on the concentration of dy e molecules in the polystyrene film is described by simple percolation theory. The synthesis of ,3'-tetrachloro-9,9'-dimethoxy-10,10'-bianth racene is reported.