Thermoelectric properties of sorted semiconducting single-walled carbon nanotube sheets

Single-walled carbon nanotubes (SWNTs), especially their semiconducting type, are promising thermoelectric (TE) materials due to their high Seebeck coefficient. In this study, the in-plane Seebeck coefficient (S), electrical conductivity (σ), and thermal conductivity (κ) of sorted semiconducting SWNT (s-SWNT) free-standing sheets with different s-SWNT purities are measured to determine the figure of merit ZT. We find that the ZT value of the sheets increases with increasing s-SWNT purity, mainly due to an increase in Seebeck coefficient while the thermal conductivity remaining constant, which experimentally proved the superiority of the high purity s-SWNT as TE materials for the first time. In addition, from the comparison between sorted and unsorted SWNT sheets, it is recognized that the difference of ZT between unsorted SWNT and high-purity s-SWNT sheet is not remarkable, which suggests the control of carrier density is necessary to further clarify the superiority of SWNT sorting for TE applications.

单壁碳纳米管（SWNTs），尤其是其半导体类型，因具有高塞贝克系数而成为有潜力的热电（TE）材料。在本研究中，对不同纯度排序的半导体SWNT（s-SWNT）自由-standing薄片的面内塞贝克系数（S）、电导率（σ）和热导率（κ）进行了测量，以确定优值ZT。我们发现，随着s-SWNT纯度的提高，薄片的ZT值也随之增加，这主要归因于塞贝克系数的增加而热导率保持恒定，这一实验结果首次证明了高纯度s-SWNT作为TE材料的优越性。此外，通过对比排序与未排序的SWNT薄片，认识到未排序SWNT与高纯度s-SWNT薄片之间的ZT差异并不显著，这表明控制载流子密度对于进一步阐明SWNT排序在TE应用中的优越性是必要的。