Thermoelectric efficiency of single-molecule junctions with long molecular linkers

TL;DR

This study theoretically investigates how the length of molecular linkers in single-molecule junctions influences thermoelectric efficiency, revealing that longer linkers can enhance ZT and that gateway states significantly impact this relationship.

Contribution

It introduces a tight-binding model to analyze the effect of linker length and gateway states on thermoelectric performance in single-molecule junctions.

Findings

ZT increases with linker length under certain conditions.

Gateway states can significantly affect ZT.

Temperature dependence of ZT shows length-controlled minima.

Abstract

We report results of theoretical studies of thermoelectric efficiency of single-molecule junctions with long molecular linkers. The linker is simulated by a chain of identical sites described using a tight-binding model. It is shown that thermoelectric figure of merit ZT strongly depends on the bridge length, being controlled by the lineshape of electron transmission function within the tunnel energy range corresponding to HOMO/LUMO transport channel. Using the adopted model we demonstrate that ZT may significantly increase as the linker lengthens, and that gateway states on the bridge (if any) may noticeably affect the length-dependent ZT. Temperature dependences of ZT for various bridge lengths are analyzed. It is shown that broad minima emerge in ZT versus temperature curves whose positions are controlled by the bridge lengths.