ACS Appl Mater Interfaces. 2015 May 13;7(18):9589-97. doi: 10.1021/acsami.5b01149. Epub 2015 May 1.
Electrical conductivity and thermopower of isotropic materials typically have inversely proportional correlation because both are strongly affected in the opposite way by the electronic carrier concentration. This behavior has been one of the major hurdles in developing high-performance thermoelectrics whose figure-of-merit enhances with large thermopower and high electrical conductivity. Here we report a promising method of simultaneously improving both properties with polyaniline (PANI) composites filled by carbon nanotubes (CNTs). With addition of double-wall CNTs (DWCNTs), the electronic mobility of PANI doped with camphorsulfonic acid (PANI-CSA) was raised from ∼0.15 to ∼7.3 cm(2)/(V s) (∼50 time improvement) while the carrier concentration was decreased from ∼2.1 × 10(21) to ∼5.6 × 10(20) cm(-3) (∼4 time reduction). The larger increase of mobility increased electrical conductivity despite the carrier concentration reduction that enlarges thermopower. The improvement in the carrier mobility could be attributed to the band alignment that attracts hole carriers to CNTs whose mobility is much higher than that of PANI-CSA. The electrical conductivity of the PANI-CSA composites with 30-wt % DWCNTs was measured to be ∼610 S/cm with a thermopower value of ∼61 μV/K at room temperature, resulting in a power factor value of ∼220 μW/(m K(2)), which is more than two orders higher than that of PANI-CSA as well as the highest among those of the previously reported PANI composites. Further study may result in high performance thermoelectric organic composites uniquely offering mechanical flexibility, light weight, low toxicity, and easy manufacturing. unlike conventional inorganic semiconductors.
各向同性材料的电导率和塞贝克系数通常呈反比关系，因为它们都受到电子载流子浓度的强烈反方向影响。这种行为一直是开发高性能热电材料的主要障碍之一，因为热电材料的优值随着塞贝克系数的增大和电导率的提高而提高。在这里，我们报告了一种很有前途的方法，即用碳纳米管（CNT）填充的聚苯胺（PANI）复合材料来同时提高这两个性能。加入双壁 CNT（DWCNT）后，掺杂樟脑磺酸的聚苯胺（PANI-CSA）的电子迁移率从约 0.15 提高到约 7.3 cm2/（Vs）（提高约 50 倍），而载流子浓度从约 2.1×1021 降低到约 5.6×1020 cm-3（降低约 4 倍）。尽管载流子浓度的降低会增大塞贝克系数，但迁移率的较大增加仍提高了电导率。载流子迁移率的提高可归因于能带排列，该排列将空穴载流子吸引到 CNT 上，而 CNT 的迁移率远高于 PANI-CSA。在 30wt% DWCNT 的 PANI-CSA 复合材料中，室温下的电导率约为 610 S/cm，塞贝克系数约为 61 μV/K，因此功率因子值约为 220 μW/（mK2），这比 PANI-CSA 高两个数量级，也高于之前报道的 PANI 复合材料中的最高值。进一步的研究可能会导致高性能的有机热电复合材料具有独特的优势，例如机械柔韧性、重量轻、低毒性和易于制造，而这是传统无机半导体所不具备的。
