Thermoelectric properties of graphene/boron nitride heterostructures

TL;DR

This study investigates the thermoelectric properties of graphene/boron nitride heterostructures using density functional theory, revealing how doping enhances thermopower and figure of merit, with potential for efficient thermoelectric devices.

Contribution

The paper demonstrates how doping in graphene/boron nitride heterostructures significantly improves thermoelectric performance, providing new insights into optimizing these materials.

Findings

Doping with TTF increases thermopower to -284 μV/K.

Doping with TCNE increases thermopower to 210 μV/K.

Figures of merit ZT up to 0.9 are achieved.

Abstract

Using density functional theory combined with a Green's function scattering approach, we examine the thermoelectric properties of hetero-nanoribbons formed from alternating lengths of graphene and boron nitride. In such structures, the boron nitride acts as a tunnel barrier, which weakly couples states in the graphene, to form mini-bands . In un-doped nanoribbons, the mini bands are symmetrically positioned relative to the Fermi energy and do not enhance thermoelectric performance significantly. In contrast, when the ribbons are doped by electron donating or electron accepting adsorbates, the thermopower S and electronic figure of merit are enhanced and either positive or negative thermopowers can be obtained. In the most favourable case, doping with the electron donor tetrathiafulvalene (TTF) increases the room-temperature thermopower to -284 {\mu}v/K and doping by the electron acceptor tetracyanoethylene (TCNE) increases S to 210 {\mu}v/K. After including both electron and phonon contributions to the thermal conductance, figures of merit ZT up to of order 0.9 are obtained.