Experimental Observation of Strong Exciton Effects in Graphene Nanoribbons

TL;DR

This study demonstrates that graphene nanoribbons exhibit exceptionally strong excitonic effects with high binding energy and ultrafast formation, highlighting their potential for advanced optoelectronic applications.

Contribution

The paper provides the first experimental observation of strong exciton effects with high binding energy and ultrafast dynamics in liquid-phase-dispersed GNRs.

Findings

Exciton binding energy up to 700 meV in GNRs

Ultrafast exciton formation with lifetimes over 100 ps

Strong Coulomb interactions in GNRs

Abstract

Graphene nanoribbons (GNRs) with atomically precise width and edge structures are a promising class of nanomaterials for optoelectronics, thanks to their semiconducting nature and high mobility of charge carriers. Understanding the fundamental static optical properties and ultrafast dynamics of charge carrier generation in GNRs is essential for optoelectronic applications. Combining THz spectroscopy and theoretical calculations, we report a strong exciton effect with binding energy up to 700 meV in liquid-phase-dispersed GNRs with a width of 1.7 nm and an optical bandgap of 1.6 eV, illustrating the intrinsically strong Coulomb interactions between photogenerated electrons and holes. By tracking the exciton dynamics, we reveal an ultrafast formation of excitons in GNRs with a long lifetime over 100 ps. Our results not only reveal fundamental aspects of excitons in GNRs (gigantic binding energy and ultrafast exciton formation etc.), but also highlight promising properties of GNRs for optoelectronic devices.