Strain Induced Thermoelectric Property Tunability of Single-Wall Carbon Nanotubes: A First-Principles Study

Abstract

Enhancement of Seebeck coefficient is crucial to fabricate high-performance thermoelectric devices for converting waste heat into electrical energy and vice-versa. Here, we used density functional theory along with the Boltzmann transport equation to study the electronic and thermoelectric properties of isolated semiconducting single-wall carbon nanotubes (SWCNTs) under compressive and tensile strain. We considered two types of zigzag SWCNTs (7,0) (typeI) and (S,0) (type-II). For type-I SWCNT, band gap and Seebeck coefficient increased with increasing the tensile strain and decreased with increasing the value of compressive strain. Whereas reverse trend was exhibited by type-II SWCNT. Our study demonstrated that electrical and thermoelectric properties of SWCNTs can be tuned by applying varying degrees of mechanical strains through external hydrostatic pressure. We tuned the value of Seebeck coefficient from $186 \mu{V}\mathrm{K}^{-1}$ to $945 \mu{V}\mathrm{K}^{-1}$ and $705\mu{V}\mathrm{K}^{-1}$ to $1020 \mu{V}\mathrm{K}^{-1}$ for (7,0) and (S,0) SWCNTs, respectively at 300 K. Furthermore, our study showed that the band gaps can be quenched resulting in semiconducting to metallic transition by applying strain along the tube axis. These intriguing features induced by strain are promising for flexible nanoelectronic device applications, such as strain sensors, energy harvesters, thermoelectric nanogenerators, and thermoelectric coolers.