POLYMERIC ANODES FOR IMPROVED POLYMER LIGHT-EMITTING DIODE PERFORMANCE

We have studied polyaniline and polyethylenedioxythiophene transparent electrodes for use as hole-injecting anodes in polymer light emitting diodes. The anodes were doped with a variety of polymer and monomer-b ased acids and cast from either water or organic solvents to determine the effect of the dopant and solvent on the hole-injection properties . We find that the anodes with polymeric dopants have improved device quantum efficiency and brightness relative to those with small molecul e dopants, independent of conductivity, solvent, or type of conducting polymer. For the most conducting polymer anodes [sigma>2(Ohm cm)(-1)] , diodes could be made without an indium tin oxide underlayer. These d iodes show substantially slower degradation. (C) 1997 American Institu te of Physics.