Department of Mechanical Engineering, Texas A&M University, College Station, Texas 77843, USA.
ACS Nano. 2010 Jan 26;4(1):513-23. doi: 10.1021/nn9013577.
The thermoelectric properties of carbon nanotube (CNT)-filled polymer composites can be enhanced by modifying junctions between CNTs using poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS), yielding high electrical conductivities (up to approximately 40000 S/m) without significantly altering thermopower (or Seebeck coefficient). This is because PEDOT:PSS particles are decorated on the surface of CNTs, electrically connecting junctions between CNTs. On the other hand, thermal transport remains comparable to typical polymeric materials due to the dissimilar bonding and vibrational spectra between CNT and PEDOT:PSS. This behavior is very different from that of typical semiconductors whose thermoelectric properties are strongly correlated. The decoupled thermoelectric properties, which is ideal for developing better thermoelectric materials, are believed to be due to thermally disconnected and electrically connected contact junctions between CNTs. Carrier transport at the junction is found to be strongly dependent on the type and concentration of stabilizers. The crucial role of stabilizers was revealed by characterizing transport characteristics of composites synthesized by electrically conducting PEDOT:PSS and insulating gum Arabic (GA) with 1:1-1:4 weight ratios of CNT to stabilizers. The influence of composite synthesis temperature and CNT-type and concentration on thermoelectric properties has also been studied. Single-walled (SW) CNT-filled composites dried at room temperature followed by 80 degrees C exhibited the best thermoelectric performance in this study. The highest thermoelectric figure of merit (ZT) in this study is estimated to be approximately 0.02 at room temperature, which is at least one order of magnitude higher than most polymers and higher than that of bulk Si. Further studies with various polymers and nanoparticles with high thermoelectric performance may result in economical, lightweight, and efficient polymer thermoelectric materials.
碳纳米管（CNT）填充聚合物复合材料的热电性能可以通过使用聚（3,4-亚乙基二氧噻吩）聚（苯乙烯磺酸盐）（PEDOT：PSS）修饰 CNT 之间的结来增强，从而在不显著改变热电势（或塞贝克系数）的情况下获得高电导率（高达约 40000 S/m）。这是因为 PEDOT：PSS 颗粒被修饰在 CNT 的表面上，从而电连接 CNT 之间的结。另一方面，由于 CNT 和 PEDOT：PSS 之间的键合和振动光谱不同，热传递仍然与典型的聚合物材料相当。这种行为与典型的半导体非常不同，典型的半导体的热电性能是强烈相关的。这种脱耦的热电性能对于开发更好的热电材料非常理想，据信是由于 CNT 之间的热隔离和电连接接触结造成的。在结处的载流子输运被发现强烈依赖于稳定剂的类型和浓度。通过用导电 PEDOT：PSS 和绝缘树胶阿拉伯胶（GA）以 CNT 与稳定剂的 1:1-1:4 重量比合成的复合材料的传输特性的表征，揭示了稳定剂的关键作用。还研究了复合材料合成温度以及 CNT 类型和浓度对热电性能的影响。在这项研究中，室温下干燥的单壁（SW）CNT 填充复合材料随后在 80°C 下干燥，表现出最佳的热电性能。在这项研究中，最高的热电优值（ZT）估计约为 0.02，室温下，至少比大多数聚合物高一个数量级，比块状 Si 高。与各种聚合物和具有高热电性能的纳米颗粒的进一步研究可能会导致经济、轻便和高效的聚合物热电材料。
