Engineering high charge transfer n-doping of graphene electrodes and its application to organic electronics

Using thermally evaporated cesium carbonate (Cs₂CO₃) in an organic matrix, we present a novel strategy for efficient n-doping of monolayer graphene and a ∼90% reduction in its sheet resistance to ∼250 Ohm sq⁻¹. Photoemission spectroscopy confirms the presence of a large interface dipole of ∼0.9 eV between graphene and the Cs₂CO₃/organic matrix. This leads to a strong charge transfer based doping of graphene with a Fermi level shift of ∼1.0 eV. Using this approach we demonstrate efficient, standard industrial manufacturing process compatible graphene-based inverted organic light emitting diodes on glass and flexible substrates with efficiencies comparable to those of state-of-the-art ITO based devices.