Enhanced thermoelectric figure of merit in vertical graphene junctions

TL;DR

This paper demonstrates that vertical graphene junctions with weak van-der Waals interactions significantly reduce phonon conductance, leading to a thermoelectric figure of merit exceeding 1 at room temperature, thus enhancing graphene device efficiency.

Contribution

It introduces a novel approach to improve thermoelectric performance in graphene by using vertical junctions that suppress phonon conductance without compromising electrical properties.

Findings

Thermoelectric figure of merit exceeds 1 at room temperature.

Phonon conductance is strongly reduced in vertical graphene junctions.

Electrical performance remains weakly affected by the junction structure.

Abstract

In this work, we investigate thermoelectric properties of junctions consisting of two partially overlapped graphene sheets coupled to each other in the cross-plane direction. It is shown that because of the weak van-der Waals interactions between graphene layers, the phonon conductance in these junctions is strongly reduced, compared to that of single graphene layer structures, while their electrical performance is weakly affected. By exploiting this effect, we demonstrate that the thermoelectric figure of merit can reach values higher than 1 at room temperature in junctions made of gapped graphene materials, for instance, graphene nanoribbons and graphene nanomeshes. The dependence of thermoelectric properties on the junction length is also discussed. This theoretical study hence suggests an efficient way to enhance thermoelectric efficiency of graphene devices.