A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription.For more information, please contact eprints@nottingham.ac.uk 1 DOI: 10.1002/((please add manuscript number)) Article type: Communication
Low-Cost and Sustainable Organic Thermoelectrics Based on LowDimensional Molecular MetalsBy Florian Huewe*, Alexander Steeger*, Kalina Kostova, Laurence Burroughs, Irene Bauer, Peter Strohriegl, Vladimir Dimitrov, Simon Woodward and Jens Pflaum* F. Huewe [ †] , A. Steeger [ †] The dimensionless figure of merit measures a material's thermoelectric performancewhere electrical conductivity (resistivity ), Seebeck coefficient/thermopower , and thermal conductivity provide the power factor = 2 . Materials with high electrical conductivity and thermopower but low thermal conductivity are desirable to maximize and hence, the thermoelectric conversion efficiency. Approximately, is inversely proportional to which in turn is related to the electronic thermal conductivity el = via the Wiedemann-Franz (WF) law.Advances in have been achieved by tuning the doping of semiconductors to maximize the [6] together with reducing the phononic contribution to thermal conduction by means of nanostructured superlattice architectures [7,8] . To overcome the inherent limitations of ordinary materials, a dimensionality reduction of the electronic system has been proposed [9] . This can lead to a violation of the WF law [10,11] and to phonon drag contributions to the thermopower [12] . Complex crystal structures, e.g. Zintl compounds [13] and skutterudites [14] , have been evaluated as good thermoelectric 3 candidates due to reduced lattice thermal conductivity and electronic band structure tunability. These optimization strategies, together with the ability for low-cost production and low-temperature processibility, have recently raised interest in organic polymers [15] , such as PEDOT:Tos, reaching = 0.25 at room temperature (RT) [4] and thus advancing the value of = 1.2 obtained for Bi2Te3 (the best RT thermoelectric material to date [7] ). Herein, quasi-1D organic conductors based on small molecules constitute a new, sustainable approach towards organic thermoelectrics that provide many of the desired electrical and thermal properties described above. Additionally, they are lightweight and thermodynamically stable allowing for portable device manufacturing and long-term usage. In comparison to organic polymers the availability of electrically high-performing p-and ntype organic conductors facilitates the construction of all-organic thermoelectric devices.As a starting point we chose two of the best p-and n-type conducting radical ion salts, TTT2I3 (TTT = Tetrathiotetracene) and (DMe-DCNQI)2Cu (DMe-DCNQI = Dimethyl-Dicyanoquinonediimine).They form macroscopic needle-like sin...
