Retained carrier-mobility and enhanced plasmonic-photovoltaics of graphene via ring-centered η6 functionalization and nano-interfacing

Abstract

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%).