Algharagholy L A A, Pope T, Lambert C J
Department of Physics, Lancaster University, Lancaster, United Kingdom. Department of Physics, College of Science, University of Sumer, Al Rifaee, Thi Qar, Iraq.
J Phys Condens Matter. 2018 Mar 14;30(10):105304. doi: 10.1088/1361-648X/aaa872.
We show that carbon-based nanostructured materials are a novel testbed for controlling thermoelectricity and have the potential to underpin the development of new cost-effective environmentally-friendly thermoelectric materials. In single-molecule junctions, it is known that transport resonances associated with the discrete molecular levels play a key role in the thermoelectric performance, but such resonances have not been exploited in carbon nanotubes (CNTs). Here we study junctions formed from tapered CNTs and demonstrate that such structures possess transport resonances near the Fermi level, whose energetic location can be varied by applying strain, resulting in an ability to tune the sign of their Seebeck coefficient. These results reveal that tapered CNTs form a new class of bi-thermoelectric materials, exhibiting both positive and negative thermopower. This ability to change the sign of the Seebeck coefficient allows the thermovoltage in carbon-based thermoelectric devices to be boosted by placing CNTs with alternating-sign Seebeck coefficients in tandem.
我们表明，碳基纳米结构材料是控制热电性的新型试验台，并且有潜力支撑新型经济高效且环保的热电材料的开发。在单分子结中，已知与离散分子能级相关的输运共振在热电性能中起关键作用，但这种共振尚未在碳纳米管（CNT）中得到利用。在这里，我们研究了由锥形碳纳米管形成的结，并证明此类结构在费米能级附近具有输运共振，其能量位置可通过施加应变来改变，从而具备调节其塞贝克系数符号的能力。这些结果表明，锥形碳纳米管形成了一类新型的双热电材料，兼具正和负的热功率。这种改变塞贝克系数符号的能力使得通过串联放置具有交替符号塞贝克系数的碳纳米管，可提高碳基热电器件中的热电压。
