Thermoelectric Properties of Organic Charge-Transfer Compounds

Abstract

We measured the thermoelectric (TE) properties of compressed pellets of various organic charge-transfer (CT) complexes, such as (TTF)(TCNQ), (BO)(TCNQ) and (ET) 2 (HCNAL), where TTF, TCNQ, BO, ET, and HCNAL represent tetrathiafulvalene, tetracyanoquinodimethane, bis(ethylenedioxy)-tetrathiafulvalene, bis(ethylenedithio)tetrathiafulvalene, and 2,5-dicyano-3,6-dihydroxy-p-benzoquinone, respectively. The metallic (TTF)(TCNQ) and semiconducting (BO)(TCNQ) complexes showed Seebeck coefficients (S) of À18 lV/K and À30 lV/K at 300 K, respectively. On the contrary, the Mott insulator (ET) 2 (HCNAL) was found to show a rather high absolute S (À116 lV/K at 300 K), the magnitude of which is comparable to those of the conventional inorganic TE materials. With increasing temperature (170 K to 300 K), the electrical conductivity was increased about two orders of magnitude while the S value was nearly constant. These results suggest that S values could be determined mainly by spin entropy (configurations) of carriers in the Mott insulator (ET) 2 (HCNAL). The magnitude of the observed S value was compared with that derived from a theoretical model (generalized Heikes formula).

Organic Thermoelectric Materials and Devices Based on p‐ and n‐Type Poly(metal 1,1,2,2‐ethenetetrathiolate)s

“…The poly[Ni x (Ni-ett)] shows a σ rt about 6.6 S cm −1 , while poly[Na x (Ni-ett)] and poly[K x (Ni-ett)] display conductivities around 40 S cm −1 . It was noted that Seebeck coefficients of these nickel complexes (except poly[Bu 4 N x (Ni-ett)]) are much higher in comparison to those highly doped conducting polymers [18,19] and charge transfer salts, [20,21] which have similar conductivities. Among these polymers, Poly[K x (Ni-ett)] possesses the highest The power output of the module is measured with different loads (Figure 3d) under various T hot and ΔT.…”

Magneto-Seebeck effect in an ITO/PEDOT:PSS/Au thin-film device

“…C Recent research on organic thermoelectric materials has focused on their unique electronic properties. [1][2][3][4][5][6][7][8][9] However the traditional semi-metals, such as bismuth and telluride alloys, still currently dominate the application of thermoelectrics, since they present remarkably high Seebeck coefficients. 10 As their thermoelectric and magneto-thermopower properties have been greatly understood, they have been widely employed in electronics and automobiles as commercialized thermoelectrics.…”

“…The inorganic/organic hybrid architecture has been developed due to the large flexibility in tuning the electric conductivity and thermal conductivity. The developed low dimensional thermoelectric hybrids exhibit quantum confinement effects 7 and can effectively reduce the thermal conduction while the electrical conduction is maintained or even enhanced as compared to pure organic thermoelectrics. 25 Moreover, through phonon scattering at interfaces, boundaries and imperfections, the nano-scale heterojunctions allow charge transport through tunneling and minimize the thermal conductivities.…”

Coordination Chemistry of 2,2′-Bipyridyl- and 2,2′:6′,2″-Terpyridyl-Substituted BEDT-TTFs: Formation of a Supramolecular Capsule Motif by the Iron(II) Tris Complex of 2,2′-Bipyridine-4-thiomethyl-BEDT-TTF

“…2 The salts have been intensively studied to gain a better understanding of their different electrical properties and the mechanisms underlying changes in those properties on variation of temperature or pressure, as well as to explore properties such as ferroelectricity 3 and thermopower. 4 For any particular counterion there can exist different stoichiometries, polymorphs and solvates, with different electrical properties.…”