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Increasing the thermopower of crown-ether-bridged anthraquinones

Research output: Contribution to journalJournal articlepeer-review

Published
<mark>Journal publication date</mark>7/11/2015
<mark>Journal</mark>Nanoscale
Issue number41
Volume7
Number of pages5
Pages (from-to)17338-17342
Publication StatusPublished
Early online date25/09/15
<mark>Original language</mark>English

Abstract

We investigate strategies for increasing the thermopower of crown-ether-bridged anthraquinones. The novel design feature of these molecules is the presence of either (1) crown-ether or (2) diaza-crown-ether bridges attached to the side of the current-carrying anthraquinone wire. The crown-ether side groups selectively bind alkali-metal cations and when combined with TCNE or TTF dopants, provide a large phase-space for optimising thermoelectric properties. We find that the optimum combination of cations and dopants depends on the temperature range of interest. The thermopowers of both 1 and 2 are negative and at room temperature are optimised by binding with TTF alone, achieving thermpowers of -600 mu V K-1 and -285 mu V K-1 respectively. At much lower temperatures, which are relevant to cascade coolers, we find that for 1, a combination of TTF and Na+ yields a maximum thermopower of -710 mu V K-1 at 70 K, whereas a combination of TTF and Li+ yields a maximum thermopower of -600 mu V K-1 at 90 K. For 2, we find that TTF doping yields a maximum thermopower of -800 mu VK-1 at 90 K, whereas at 50 K, the largest thermopower (of -600 mu V K-1) is obtain by a combination TTF and K+ doping. At room temperature, we obtain power factors of 73 mu W m(-1) K-2 for 1 (in combination with TTF and Na+) and 90 mu W m(-1) K-2 for 2 (with TTF). These are higher or comparable with reported power factors of other organic materials.