Enhancing thermoelectric figure-of-merit by low-dimensional electrical transport in phonon-glass crystals

TL;DR

This paper proposes using low-dimensional electronic structures within bulk phonon-glass crystals to enhance thermoelectric efficiency, demonstrating a significant figure of merit through computational methods without material optimization.

Contribution

It introduces a novel approach of employing low-dimensional electronic structures in bulk phonon-glass crystals to improve thermoelectric performance, validated by first-principles calculations.

Findings

Achieved a maximum room-temperature ZT of 1.48 at optimal doping.

Identified Bis-Dithienothiophene molecular crystal as a promising candidate.

Validated the approach without needing material parameter optimization.

Abstract

Low-dimensional electronic and glassy phononic transport are two important ingredients of highly-efficient thermoelectric material, from which two branches of the thermoelectric research emerge. One focuses on controlling electronic transport in the low dimension, while the other on multiscale phonon engineering in the bulk. Recent work has benefited much from combining these two approaches, e.g., phonon engineering in low-dimensional materials. Here, we propose to employ the low-dimensional electronic structure in bulk phonon-glass crystal as an alternative way to increase the thermoelectric efficiency. Through first-principles electronic structure calculation and classical molecular dynamics simulation, we show that the $\pi$-$\pi$ stacking Bis-Dithienothiophene molecular crystal is a natural candidate for such an approach. This is determined by the nature of its chemical bonding. Without any optimization of the material parameter, we obtain a maximum room-temperature figure of merit, $ZT$, of $1.48$ at optimal doping, thus validating our idea.