Multiwalled carbon nanotube sheets as transparent electrodes in high brightness organic light-emitting diodes

We have fabricated efficient organic light emitting diodes using strong, transparent carbon nanotube (CNT) sheets as the hole-injecting anode. These devices show a brightness of 4500 cd/m(2) and current efficiency near 2.5 cd/A, which is close to the efficiency we achieve with a similar device, which uses indium tin oxide (ITO) as the anode. We demonstrate that proper planarization of the electrode using the water-soluble polymer poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) is necessary for achieving high efficiency and can be accomplished by spin casting multiple layers. We believe that increased conductivity of the sheets could lead to CNT-based devices with efficiencies exceeding those on ITO.