Submicrometer-sized organic light emitting diodes with a triphenylamine-containing polycarbonate as a guest molecule in a polymer blend

We fabricated submicrometer-sized organic light emitting diodes (OLED) with bright emission using a polymer blend. The cell structure was composed of ITO (indium-tin oxide)/hole transport layer (polymer blend layer)/emitter layer/MgAg. We used poly (methyl methacrylate) (PMMA) as an inert host material and N,N′-diphenyl-N,N′-bis(3-methylphenyl)- [1,1′-biphenyl]-4,4′-diamine-polycarbonate (PC-TPD) as a guest material. The PC-TPD formed submicrometer-sized spherical domains, actually prolate spheroids, in the PMMA host layer. With 2 wt% of PC-TPD, the domain diameters were around 200 nm according to atomic force microscopy (AFM) observation. The OLED including such a blend structure appeared as an array of bright submicrometer-sized electroluminescence spots. The number of working diodes exceeded four million per square centimeter.