Highly fluorescent molecular organic composites for light-emitting diodes

Organic films of tris-(8-hydroxyquinolinato) aluminum (III) and N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine doped with highly fluorescent molecules were prepared by vacuum deposition. Optical absorption and photoluminescence spectra of the composites were measured as a function of dopant concentration. These films were also used as the emitting layer in light-emitting diodes, where their electroluminescence spectra was studied as a function of dopant concentration. Color tunability from the blue-green to the red-orange based on variation in the fluorescent molecule and dopant concentration was attained, and quantum efficiencies were found to be enhanced upon doping of the emitter layer.