Tuning the Work Function of Graphene-on-Quartz with a High Weight Molecular Acceptor

Ultraviolet and X-ray photoelectron spectroscopies in combi- nation with density functional theory (DFT) calculations were used to study the change in the work function (Φ) of graphene, supported by quartz, as induced by adsorption of hexaazatriphenylene−hexacarbonitrile (HATCN). Near edge X-ray absorption fine structure spectroscopy (NEXAFS) and DFT modeling show that a molecular-density-dependent reorientation of HATCN from a planar to a vertically inclined adsorption geometry occurs upon increasing surface coverage. This, in conjunction with the orientation- dependent magnitude of the interface dipole, allows one to explain the evolution of graphene Φ from 4.5 eV up to 5.7 eV, rendering the molecularly modified graphene-on-quartz a highly suitable hole injection electrode.