Controlled surface oxidation of multi-layered graphene anode to increase hole injection efficiency in organic electronic devices

Ultraviolet ozone (UVO) surface treatment of graphene changes its sp(2)-hybridized carbons to sp(3)-bonded carbons, and introduces oxygen-containing components. Oxidized graphene has a finite energy band gap, so UVO modification of the surface of a four-layered graphene anode increases its surface ionization potential up to similar to 5.2 eV and improves the hole injection efficiency (eta) in organic electronic devices by reducing the energy barrier between the graphene anode and overlying organic layers. By controlling the conditions of the UVO treatment, the electrical properties of the graphene can be tuned to improve eta. This controlled surface modification of the graphene will provide a way to achieve efficient and stable flexible displays and solid-state lighting.