Interfacial electronic structures between fullerene and multilayer graphene for n-type organic semiconducting devices

The interfacial electronic structure of fullerene (C60) deposited on a multilayer graphene (MLG) film was measured using in situ ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy. The energy level alignment at the interface of C60/MLG was estimated by the shifts in the highest occupied molecular orbital (HOMO) and the vacuum level during step-by-step deposition of C60 on the MLG. The shift of the HOMO level indicates that there is a small band bending at the interface of C60/MLG. The vacuum level was shifted 0.06 eV toward the low binding energy with additional C60 on the MLG. The measurements reveal that the height of the electron injection barrier is 0.59 eV, while the hole injection barrier height is 2.01 eV. We present a complete interfacial energy level diagram for C60/MLG.