Role of Edge Engineering in Photoconductivity of Graphene Nanoribbons

Abstract

The effect of edge engineering of graphene nanoribbons (GNRs) on their ultrafast photoconductivity is investigated. Three different GNRs were fabricated by bottom-up synthesis in the liquid phase, where structure, width, and edge planarity could be controlled chemically at the atomic level. The charge carrier transport in the fabricated GNRs was studied on the ultrafast, sub-picosecond time scale using time-resolved terahertz spectroscopy, giving access to the elementary parameters of carrier conduction. While the variation of the side chains does not alter the photoconductive properties of GNRs, the edge structure has a strong impact on the carrier mobility in GNRs by affecting the carrier momentum scattering rate. Calculations of the ribbon electronic structure and theoretical transport studies show that phonon scattering plays a significant role in microscopic conduction in GNRs with different edge structures. A comparison between theory and experiment indicates that the mean free path of charge carriers in the nanoribbons amounts to typically ∼20 nm.

Polycyclic aromatic hydrocarbons in the graphene era

“…Single-GNR transistor devices demonstrated the semiconducting properties of GNR 97, and thin-film devices exhibited remarkable chemical sensing capability toward NO 2 gas with limits of detection down to parts per billion levels [136]. Nevertheless, the charge-carrier mobilities obtained from the GNR-based devices were much lower than the intrinsic values as evaluated by ultrafast terahertz photoconductivity analysis and theoretical calculations [137,138]. The poor device performance is presumably due to the high contact resistance between the electrodes and GNRs, requiring improved device fabrication.…”

Terahertz Spectroscopy of Nanomaterials: a Close Look at Charge‐Carrier Transport

“…Their response in the THz range thus can be described as the one of polarizable particles in quasistatic regime embedded in an insulating matrix; this leads to a negligible real part of the conductivity, and a linearly decreasing imaginary part. [135] Some of these analyses further combine the Drude-Smith model with an effective medium approximation; this approach was used for example in order to describe the response of silicon nanowires and nanocrystals, [136] ZnO nanowires, [137] ZnO/In 2 S 3 core/shell nanorod heterojunctions, [138] or silver nanowires. [112,113] A transition from an extended electron state into a localized exciton state was observed in CdSe nanorods.…”

Unraveling Photoexcited Charge Transfer Pathway and Process of CdS/Graphene Nanoribbon Composites toward Visible‐Light Photocatalytic Hydrogen Evolution

“…While the vast majority of studies on graphene cocatalysts are limited to micrometer‐sized ones, far less information is available on graphene nanoribbons (abbreviated as GNRs) with less than 100 nm in size. In comparison with conventional graphene, GNRs feature less local density of defects but more active edges to enhance electrical conductibility, in addition to inherent properties of extraordinary specific surface area, excellent light absorption and good chemical stability . Hence, combining GNRs and CdS NPs is expected to effectively promote photocatalytic performance of CdS NPs.…”