Thermoelectric figure of merit of tau-type conductors of several donors

TL;DR

This study measures the thermoelectric figure of merit (ZT) of various tau-type organic conductors, finding that specific donor molecules yield higher ZT values at low temperatures, with the best donor identified as EDT-S,S-DMEDT-TTF.

Contribution

The paper provides the first systematic measurement of ZT in tau-type organic conductors, comparing different donors and identifying the most effective for thermoelectric performance.

Findings

Maximum ZT of 2.7×10^{-2} at 155 K for one compound.

EDT-S,S-DMEDT-TTF donor yields the highest ZT among tested donors.

ZT values are temperature-dependent, peaking at low temperatures.

Abstract

Dimensionless thermoelectric figure of merit $ZT$ is investigated for two-dimensional organic conductors $\tau-(EDO-S,S-DMEDT-TTF)_2(AuI_2)_{1+y}$, $\tau$-(EDT-S,S-DMEDT-TTF)_2(AuI_2)_{1+y}$ and $\tau$-(P-S,S-DMEDT-TTF)_2(AuI_2)_{1+y}$ ($y \le 0.875$), respectively. The $ZT$ values were estimated by measuring electrical resistivity, thermopower and thermal conductivity simultaneously. The largest $ZT$ is 2.7 $\times$ 10$^{-2}$ at 155 K for $\tau-(EDT-S,S-DMEDT-TTF)_2(AuI_2)_{1+y}$, 1.5 $\times$ 10$^{-2}$ at 180 K for $\tau-(EDO-S,S-DMEDT-TTF)_2(AuI_2)_{1+y}$ and 5.4 $\times$ 10$^{-3}$ at 78 K for $\tau-(P-S,S-DMEDT-TTF)_2(AuI_2)_{1+y}$, respectively. Substitution of the donor molecules fixing the counter anion revealed EDT-S,S-DMEDT-TTF is the best of the three donors to obtain larger $ZT$.