Linkoping University, Department of Science and Technology, Organic Electronics, SE-601 74 Norrkoping, Sweden.
Linköping University, Department of Physics, Chemistry and Biology, S-581 83 Linköping, Sweden.
Nat Mater. 2014 Feb;13(2):190-4. doi: 10.1038/nmat3824. Epub 2013 Dec 8.
Polymers are lightweight, flexible, solution-processable materials that are promising for low-cost printed electronics as well as for mass-produced and large-area applications. Previous studies demonstrated that they can possess insulating, semiconducting or metallic properties; here we report that polymers can also be semi-metallic. Semi-metals, exemplified by bismuth, graphite and telluride alloys, have no energy bandgap and a very low density of states at the Fermi level. Furthermore, they typically have a higher Seebeck coefficient and lower thermal conductivities compared with metals, thus being suitable for thermoelectric applications. We measure the thermoelectric properties of various poly(3,4-ethylenedioxythiophene) samples, and observe a marked increase in the Seebeck coefficient when the electrical conductivity is enhanced through molecular organization. This initiates the transition from a Fermi glass to a semi-metal. The high Seebeck value, the metallic conductivity at room temperature and the absence of unpaired electron spins makes polymer semi-metals attractive for thermoelectrics and spintronics.
聚合物是重量轻、灵活、可溶液处理的材料，有望用于低成本的印刷电子产品以及大规模生产和大面积应用。之前的研究表明，它们可以具有绝缘、半导体或金属特性；在这里，我们报告说聚合物也可以是半金属。半金属的例子有铋、石墨和碲化物合金，它们没有能隙，费米能级处的态密度非常低。此外，与金属相比，它们通常具有更高的塞贝克系数和更低的热导率，因此适用于热电应用。我们测量了各种聚（3,4-乙撑二氧噻吩）样品的热电性质，并观察到当通过分子组织增强电导率时，塞贝克系数显著增加。这引发了从费米玻璃到半金属的转变。高的塞贝克系数、室温下的金属电导率以及不成对电子自旋的缺失使得聚合物半金属在热电学和自旋电子学方面具有吸引力。
