Electronic structure of graphene/MoO3/CuPc interfaces

The interfacial electronic structures of graphene/copper phthalocyanine (CuPc) modified with MoO3 interlayers were investigated using x-ray and ultraviolet photoelectron spectroscopy. Strong p-doping effect has been observed on graphene due to deposition of MoO3 films, causing formation of surface dipole (eD) and shift of graphene Dirac point, and consequently altering the charge transfer at graphene/CuPc interface. The ionization energy of CuPc on the graphene/MoO3 substrate is about 4.97 eV. The interfacial energy level alignments are estimated based on the experimental photoelectron spectroscopy data. Finally, the present experimental data indicate that the height of the electron and hole injection barriers from CuPc to graphene/MoO3 are 1.98 and 0.32 eV, respectively.