Bright Electroluminescence from Single Graphene Nanoribbon Junctions

Abstract

Thanks to their highly tunable band gaps, graphene nanoribbons (GNRs) with atomically precise edges are emerging as mechanically and chemically robust candidates for nanoscale light emitting devices of modulable emission color. While their optical properties have been addressed theoretically in depth, only few experimental studies exist, limited to ensemble measurements and without any attempt to integrate them in an electronic-like circuit. Here we report on the electroluminescence of individual GNRs suspended between the tip of a scanning tunneling microscope (STM) and a Au(111) substrate, constituting thus a realistic optoelectronic circuit. Emission spectra of such GNR junctions reveal a bright and narrow band emission of red light, whose energy can be tuned with the bias voltage applied to the junction, but always lying below the gap of infinite GNRs. Comparison with ab initio calculations indicates that the emission involves electronic states localized at the GNR termini. Our results shed light on unpredicted optical transitions in GNRs and provide a promising route for the realization of bright, robust, and controllable graphene-based light-emitting devices.

A Review on Graphene-Based Light Emitting Functional Devices

“…At higher voltage (V > 1.9 V), no further spectral features were observed. ( c ) and ( e ) confirm the shift in emission line as a function of Z and V, respectively [ 140 ].…”

“…Particularly, the EL effect has also been reported from graphene-based materials. The EL footprints have been demonstrated from single to a few layers of graphene structure [ 57 ] such as carbon nanotubes [ 139 ], carbon nanoribbons [ 140 ], and quantum dots [ 141 ].…”

“…The bright and narrowband emission of red light is obtained from the GNRs junction, where the emission spectra can be tuned via the biased voltage applied at the junction, but it lies below the bandgap of infinite GNRs. The Ab initio calculation reveals that the emission implicates the localized energy states at GNR termini [ 140 ], where the emission spectra of GNRs strongly depends on the nature of GNRs and STM tip connection. In the case of covalent bonding, a sharp and intense luminescent peak (40 m eV) was observed, whose energy can be controlled by the distance between tip and surface as well as applied voltage.…”

A Universal Length-Dependent Vibrational Mode in Graphene Nanoribbons

“…11,12 First experiments with GNRs incorporated into devices have shown that the ribbon length as well as their overall integrity are essential for realizing the inherent potential of this material. 13,14 However, methods suited to estimate the length of the GNRs after transfer onto device substrates are lacking.…”

How Structural Defects Affect the Mechanical and Electrical Properties of Single Molecular Wires

“…Introducing defects in two-dimensional materials is therefore of interest for future applications in nanotechnology where individual carbon-based molecular components are linked electrically and ensure at the same time enhanced flexibility in the architecture of the final circuits. In addition, these defects might also be used to locally tune the electronic or optical properties of the molecular wire [46], similar to semiconductor devices.…”