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Connectivity-driven bi-thermoelectricity in heteroatom-substituted molecular junctions

Research output: Contribution to journalJournal article

Published
<mark>Journal publication date</mark>26/03/2018
<mark>Journal</mark>Physical Chemistry Chemical Physics
Issue number14
Volume20
Number of pages8
Pages (from-to)9630-9637
Publication statusPublished
Early online date12/03/18
Original languageEnglish

Abstract

To improve the thermoelectric performance of molecular junctions formed by polyaromatic hydrocarbon (PAH) cores, we present a new strategy for enhancing their Seebeck coefficient by utilizing connectivities with destructive quantum interference combined with heteroatom substitution. Starting from the parent PAH, with a vanishing mid-gap Seebeck coefficient, we demonstrate that the corresponding daughter molecule obtained after heteroatom substitution possesses a non-zero, mid-gap Seebeck coefficient. For the first time, we demonstrate a “bi-thermoelectric” property, where for a given heteroatom and parent PAH, the sign of the mid-gap Seebeck coefficient depends on connectivity and therefore the daughter can exhibit both positive and negative Seebeck coefficients. This bi-thermoelectric property is important for the design of tandem thermoelectric devices, where materials with both positive and negative Seebeck coefficients are utilized to boost the thermovoltage. Simple parameter-free rules for predicting the Seebeck coefficient of such molecules are presented, which form a powerful tool for designing efficient molecular thermoelectric devices.