Energy Level Alignment and Charge Carrier Mobility in Noncovalently Functionalized Graphene

Abstract

Density functional theory calculations have been performed to assess the electronic structure of graphene overlaid with a monolayer of electro-active conjugated molecules, being either electron donors or electron acceptors. Such a noncovalent functionalization results in a work function modification that scales with the amount of electron transfer from or to graphene, in line with the formation of an interfacial dipole. The charge transfer is accompanied by a pinning of the donor HOMO/acceptor LUMO around the Fermi level and a shift in the vacuum level. The use of the Boltzmann transport equation combined with the deformation potential theory shows that large charge carrier mobilities are maintained upon noncovalent functionalization of graphene, thereby suggesting that molecular doping is an attractive approach to design conductive graphene electrodes with tailored work function