【作者】 石文； 王冬； 帅志刚；

【Author】 Wen Shi;D.Wang;Z.Shuai;MOE Key Laboratory of Organic Optoelectronics and Molecular Engineering, Department of Chemistry, Tsinghua University;

【机构】 清华大学化学系有机光电子与分子工程教育部重点实验室；

【摘要】 精确控制掺杂浓度是提高热电优值的有效方法之一。我们基于扩展的能带模型,采用玻尔兹曼输运方程,综合考虑声子散射和杂质散射的竞争,并结合第一性原理计算,定量阐述了聚合物PEDOT中掺杂浓度对热电转换过程以及载流子输运的影响^[1]。随着掺杂浓度的提高,聚合物由半导性向金属性转变。我们发现在掺杂的PEDOT:Tos中抗衡离子导致的带电杂质散射机制占主导地位,轻掺杂PEDOT:Tos的迁移率、塞贝克系数和功率因子和实验优化结果一致^[2,3],重掺杂PEDOT:Tos的热电性质差很多。另一方面,理想的PEDOT晶体中热电输运性质的各向异性很高,沿链方向的功率因子比沿堆积方向高至少一个数量级,但通过非平衡分子动力学方法对晶格热输运过程进行模拟,我们发现晶格热导的各向异性有两个数量级。因此,为提高沿链方向的热电优值,我们提出缩短链长,使其小于声子的平均自由程,但大于电子的平均自由程,并引入一定程度的结构无序,使其成为声子玻璃,同时不影响电子输运。更多还原

【Abstract】 Tuning carrier concentration via chemical doping has been recognized as one of the most successful strategies to optimize the performance of thermoelectric materials.Here, we investigated doping effects on thermoelectric properties of PEDOT:Tos by incorporating two scattering mechanisms of charge carriers, namely, acoustic phonon scattering and charged impurity scattering with the counter-ions ^[3].We corroborate that PEDOT exhibits a semiconductor-to-metal transition with an increase in the doping level.We find that the ionized impurity scattering dominates over the acoustic phonon scattering in the doped PEDOT, and the lightly doped one exhibits mobility, Seebeck coefficient and power factors in reasonable agreement with the experimental data.In addition, by shortening polymer chains to below the phonon mean free path and introducing structural disorder, lattice thermal conductivity is significantly reduced, and the figure of merit is improved by at least one order of magnitude.更多还原