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°, with AC‐OEL device power efficiencies of ≈22 lm W−1 at luminances of ≈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. Nanocomposite cathode structures—in this case metals together with multiwalled nanotubes—with the aim of combining mechanical and electronic properties to achieve better performance in an organic flexible are examined. A flexible high‐efficiency alternating current (AC) driven field‐induced polymer electroluminescent) device is chosen as the platform system with the understanding that this approach to organic devices clearly points to organic light emitting diodes, organic thin‐film transistors, and other flexible systems.