Edge currents and nanopore arrays in zigzag and chiral graphene nanoribbons as a route toward high-$ZT$ thermoelectrics

TL;DR

This paper demonstrates that nanopore arrays in zigzag and chiral graphene nanoribbons can significantly enhance thermoelectric efficiency by reducing phonon heat transport while preserving edge electronic currents, achieving high ZT values.

Contribution

It introduces a novel design of nanopore-embedded graphene nanoribbons that optimizes thermoelectric performance by selectively suppressing phononic heat conduction without impairing electronic edge currents.

Findings

Maximum ZT of ~11 at liquid nitrogen temperature.

Maximum ZT of ~4 at room temperature.

Efficient thermoelectric devices achieved in ~1 μm long GNRs.

Abstract

We analyze electronic and phononic quantum transport through zigzag or chiral graphene nanoribbons (GNRs) perforated with an array of nanopores. Since local charge current profiles in these GNRs are peaked around their edges, drilling nanopores in their interior does not affect such edge charge currents while drastically reducing heat current carried by phonons in sufficiently long wires. The combination of these two effects can yield highly efficient thermoelectric devices with maximum $ZT \simeq 11$ at liquid nitrogen temperature and $ZT \simeq 4$ at room temperature achieved in $\sim 1$ $\mu$m long zigzag GNRs with nanopores of variable diameter and spacing between them. Our analysis is based on the $\pi$-orbital tight-binding Hamiltonian with up to third nearest-neighbor hopping for electronic subsystem, the empirical fourth-nearest-neighbor model for phononic subsystem, and nonequilibrium Green function formalism to study quantum transport in both of these models.