Flexible organic light-emitting diodes with transparent carbon nanotube electrodes: problems and solutions

We study in detail here the application of transparent, conductive carbon single-wall nanotube (SWNT) networks as electrodes in flexible organic light-emitting diodes (FOLEDs). Overall comparisons of these networks to the commonly used electrodes poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and indium tin oxide (ITO) are made, and SWNT networks are shown to have excellent optical and superior mechanical properties. The effects of protruding nanotubes, rough surface morphology, and SWNT network-adjacent layer dewetting are shown to be problematic, and approaches for addressing these issues are identified. The mechanical properties of SWNT networks and ITO are compared, and SWNT networks are shown to exhibit more durable sheet conductance under bending, which leads to bendable FOLEDs. We demonstrated FOLEDs with SWNT network anodes that exhibit outstanding light output and meet display requirements. SWNT-based FOLEDs show comparable lifetime performances to ITO-based devices. The promise and the remaining challenges for implementing SWNT networks in organic light-emitting diodes are discussed.