Enhancement of thermoelectric performance in Graphene/BN heterostructures

TL;DR

This study demonstrates that graphene/BN heterostructures exhibit significantly enhanced thermoelectric performance due to phonon mismatch and bandgap effects, achieving high ZT values through atomistic simulations.

Contribution

The paper introduces a novel approach to improve thermoelectric efficiency in graphene/BN heterostructures by engineering phonon and electron transport properties.

Findings

ZT > 0.8 achievable in perfect structures

ZT up to 1.48 with vacancies in the channel

Phonon mismatch reduces thermal conductance

Abstract

The thermoelectric properties of in plane heterostructures made of Graphene and hexagonal Boron Nitride (BN) have been investigated by means of atomistic simulation. The heterostructures consist in armchair graphene nanoribbons to the sides of which BN flakes are periodically attached. This arrangement generates a strong mismatch of phonon modes between the different sections of the ribbons, which leads to a very small phonon conductance, while the electron transmission is weakly affected. In combination with the large Seebeck coefficient resulting from the BN-induced bandgap opening or broadening, it is shown that large thermoelectric figure of merit ZT > 0.8 can be reached in perfect structures at relatively low Fermi energy, depending on the graphene nanoribbon width. The high value ZT = 1.48 may even be achieved by introducing appropriately vacancies in the channel, as a consequence of further degradation of the phonon conductance.