Layered, Nanonetwork Composite Cathodes for Flexible, High-Efficiency, Organic Light Emitting Devices

In this work, the application of an aluminum (Al)/multiwall carbon nanotube (MWCNT)/Al, multilayered electrode to flexible, high-efficiency, alternating current driven organic electroluminescent devices (AC-OEL), is reported. The electrode is fabricated by sandwiching a spray-cast nanonetwork film of MWCNTs between two evaporated layers of Al. The resulting composite film facilitates a uniform charge distribution across a robust crack-free electrode under various bending angles. It is demonstrated that these composite electrodes stabilize the power efficiency of flexible devices for bending angles up to 120 degrees, with AC-OEL device power efficiencies of approximate to 22 lm W-1 at luminances of approximate to 4000 cd m(-2) (using no output coupling). Microscopic examination of the Al/MWCNTs/Al electrode after bending of up to 1300 cycles suggests that the nanotubes significantly enhance the mechanical properties of the thin Al layers while providing a moderate modification to the work function of the metal. While the realization of robust, high-brightness, and high-efficiency AC-OEL devices is potentially important in their future lighting applications, it is anticipated that this to also have significant impact in standard organic light emitting diodes lighting applications.