Molecular Arrangement and Charge Transfer in C₆₀/Graphene Heterostructures

Charge transfer at the interface between dissimilar materials is at the heart of electronics and photovoltaics. Here we study the molecular orientation, electronic structure, and local charge transfer at the interface region of C₆₀ deposited on graphene, with and without supporting substrates such as hexagonal boron nitride. We employ ab initio density functional theory with van der Waals interactions and experimentally characterize interface devices using high-resolution transmission electron microscopy and electronic transport. Charge transfer between C₆₀ and the graphene is found to be sensitive to the nature of the underlying supporting substrate and to the crystallinity and local orientation of the C₆₀. Even at room temperature, C₆₀ molecules interfaced to graphene are orientationally locked into position. High electron and hole mobilities are preserved in graphene with crystalline C₆₀ overlayers, which has ramifications for organic high-mobility field-effect devices.