Significantly enhanced thermoelectric performance of molecular junctions by the twist angle dependent phonon interference effect

Abstract

Suppressing phonon thermal conductance is one of the most important ways to improve the thermoelectric efficiency. In the present work, we theoretically analyze the phonon transport properties in the intermediately coupled molecular junction. We show that the twist angle can serve as an independent degree of freedom to manipulate phonon interference and then more precisely regulate the thermal conductance of molecular junctions. Moreover, the phonon mode-resolved calculation indicates that the conduction of in-plane phonon modes is strongly blocked, and only the out-of-plane phonon modes can be transported through the molecular junction. This makes it possible to further suppress the phonon thermal conductance with the twist angle and then significantly improve the thermoelectric figure-of-merit of intermediately coupled molecular junctions. This result suggests a more convenient way to manipulate heat transport, which has potential applications in phononic and thermoelectric molecular devices.