Researchers from Philips, Graphenea and the University of Cambridge developed a monochrome OLED device that uses graphene as the transparent conductor layer. They report that the graphene-based TC outperforms that state-of-the-art ITO solutions currently used for OLED panels.
ITO is the most popular material for transparent conductors in displays and solar cells, but it is expensive, rare and brittle, and a lot of companies are developing alternatives - based on silver, carbon or other materials.
Graphene by itself is not a good electrode material because the concentration of the charge carriers is low - which means that you need to dope it with excess carriers - while leaving it flexible and transparent. To achieve that, the team used a metal oxide film (molybdenum trioxide, MoO3) as an intermediate layer between the graphene and the OLED layers. The graphene was produced using a CVD process. By optimizing the MoO3 thickness, the researchers were able to achieve excellent power efficiency - better than the ITO reference device.
The work was performed as part of the EU project GRAFOL, aimed at roll-to-roll mass production of graphene.