Layer-by-Layer Fabrication of Fullerene-Intercalated Orthogonal Molecular Architectures Enhances Thermoelectric Behavior of Graphene-Based Nanodevices.

Despite the significant potential of molecular-scale devices for miniaturized electronics and energy conversion applications, conventional self-assembled monolayers (SAMs) exhibit limitations in simultaneously optimizing electrical conductivity and thermopower due to constrained electronic pathway modulation. This study demonstrates a molecular engineering strategy employing a discretely arranged conjugated molecular backbone to construct ordered cage-like supramolecular cavities, enabling controlled intercalation of fullerene within bipyridine-based SAMs grown on graphene-substrates. Quartz crystal microbalance and atomic force microscopy measurements confirmed the structural integrity of the fullerene-trapped SAMs. Notably, intercalation efficiency was significantly enhanced upon incorporation of an additional zinc tetraphenylporphyrin (ZnTPP) "cap" on top of SAMs, which prevented the loss of fullerene trapped within the cages. Electrical characterization via Eutectic Gallium-Indium (EGaIn)-probe measurements revealed that fullerene-intercalated SAMs exhibited an 8.3-fold higher normalized conductance compared to unintercalated counterparts, without reducing the Seebeck coefficient. Theoretical calculations attributed this enhancement to fullerene-induced Fano-resonance near the Fermi level, which amplified electron transmission. The Seebeck coefficient reached ∼60 µV K through series interface of "slippery" pyridine-zinc coordination and ZnTPP-graphene π-π coupling, while fullerene doping resulted in a similar magnitude. This cage-like intercalation strategy proves effective for decoupling electrical conductivity and the Seebeck coefficient of SAMs, providing a robust approach for synergistic thermoelectric parameter optimization in molecular junctions.