Direct laser writing of flexible graphene field emitters

We report on the simple fabrication of highly efficient solution-processable, flexible graphene-based field emission (FE) cathodes via direct laser writing of emitting pixels on reduced graphene oxide (rGO) films deposited onto rGO:poly(3-hexylthiophene) (P3HT) composite layers. Laser processing gives rise to a pronounced vertical alignment of rGO bundles perpendicular to the substrate, while at the same time sharp graphene edges are protruding out of the bundle. The laser-fabricated cathodes exhibit outstanding FE properties with a turn-on field of as low as ∼0.6 V/μm and a field enhancement factor of 8900, which are the best reported to date for rGO FE cathodes. At the same time, the cathodes exhibit stable operation under extensive and repetitive bending, a critical requirement for every flexible technology. The flexible and solution-processable, graphene-based, technology developed could be useful for diverse potential applications including field emission displays, biochemical sensors as well as solar cell and battery electrodes.