Retained Carrier-Mobility and Enhanced Plasmonic-Photovoltaics of Graphene Via Ring-Centered η6 Functionalization and Nano-Interfacing

Binding graphene with auxiliary nanoparticles for plasmonics, photovoltaics, and/or optoelectronics, while retaining the trigonal-planar bonding of sp² hybridized carbons to maintain its carrier-mobility has remained a challenge. The conventional nanoparticle-incorporation route for graphene is to create nucleation/attachment sites via ‘carbon-centered’ covalent functionalization, which changes the local hybridization of carbon atoms from trigonal-planar sp² to tetrahedral sp³. This disrupts the lattice planarity of graphene, thus dramatically deteriorating its mobility and innate superior properties. Here, we show large-area, vapor-phase, ‘ring-centered’ hexahapto (η⁶) functionalization of graphene to create nucleation-sites for silver nanoparticles (AgNPs) without disrupting its sp² character. This is achieved by the grafting of chromium tricarbonyl [Cr(CO)₃] with all six carbon atoms (sigma-bonding) in the benzenoid ring on graphene to form an (η⁶-graphene)Cr(CO)₃ complex. This non-destructive functionalization preserves the lattice continuum with a retention in charge carrier mobility (9% increase at 10 K); and with AgNPs attached on graphene/n-Si solar cells, we report an ~11-fold plasmonic-enhancement in the power conversion efficiency (1.24%).