Thermoelectric properties of finite two dimensional triangular lattices coupled to electrodes

TL;DR

This study investigates the thermoelectric properties of finite two-dimensional triangular lattices coupled to electrodes, revealing electron-hole asymmetry and conditions for optimizing power factor for energy harvesting applications.

Contribution

It introduces a Green's function approach to analyze ballistic transport in 2D TLs and highlights the asymmetric behavior of the power factor between electrons and holes.

Findings

Maximum power factor for electrons exceeds that for holes.

Optimal power factor occurs when the chemical potential is near the band edge.

Enhancement of power factor is due to increased electrical conductance and constant Seebeck coefficient.

Abstract

Novel intrinsic two-dimensional materials have attracted many researchers' attention. The unusual transport and optical properties of these materials originate mainly from triangular lattices (TLs). Therefore, the application of energy harvesting calls for a study of the thermoelectric properties of 2D TLs coupled to electrodes. The transmission coefficient of 2D TLs is calculated by using the Green's function technique to treat ballistic transports. Especially important among our findings is the electron-hole asymmetric behavior of the power factor ($PF$). Specifically, the maximum $PF$ of electrons is significantly larger than that of holes. At room temperature, the maximum $PF$ of electrons is dictated by the position of the chemical potential of electrodes near the band edge of TLs. The enhancement of $PF$ with increasing electronic states results from the enhancement of electrical conductance and constant Seebeck coefficient. When the band gap is ten times larger than the thermal energy, it is appropriate to make one-band model predictions for thermoelectric optimization.