Design of efficient vdW thermionic heterostructures from first principles

TL;DR

This paper investigates thermionic transport in graphene/phosphorene heterostructures using first-principles calculations, revealing how layering influences heat and charge transport, with implications for nanoscale cooling devices.

Contribution

It introduces a first-principles approach to analyze thermionic transport in vdW heterostructures and demonstrates the transition from tunneling to thermionic dominated transport with added layers.

Findings

Quantum tunneling dominates in monolayer phosphorene.

Adding layers switches transport to thermionic dominance.

Proposed device achieves thermionic coefficient of 18.5 at 600 K.

Abstract

This work is the first step towards understanding thermionic transport properties of graphene/phosphorene/graphene van der Waals heterostructures in contact with gold electrodes by using density functional theory based first principles calculations combined with real space Green's function formalism. We show that for monolayer phosphorene in the heterostructure, quantum tunneling dominates the transport. By adding more phosphorene layers, one can switch from tunneling dominated transport to thermionic dominated transport, resulting in transporting more heat per charge carrier, thus, enhancing the cooling coefficient of performance. The thermionic coefficient of performance for the proposed device is 18.5 at 600 K corresponding to an equivalent ZT of 0.13, which is significant for nanoscale devices.