Tunable power factor in fluorine-doped single-walled carbon nanotubes

Abstract

Herein, we present a tunable axial power factor (Pzz) in a nondegenerate fluorine-doped single-walled carbon nanotube (FSWCNT) using a tractable analytical approach. We derived the expressions for the electrical conductivity (σ), thermopower (α), and power factor (P) as a function of temperature. Additionally, we investigated the influence of doping concentration (no), constant electric field (Eo), and overlapping integrals (Δs and Δz) on their behavior. The intensity of the axial power factor (Pzz) and the operational temperature range can be tuned using the constant electric field, doping (carrier), and overlapping integrals, respectively. Applying the temperature field to the FSWCNT induces high-frequency carrier dynamics that critically depend on the magnitude of the temperature gradient. There exist two dynamic regimes that depend on the temperature gradient and carrier’s initial position. The carrier drifts through the FSWCNT and is allowed to perform drifting periodic orbits (in THz frequencies), resulting in the resonant enhancement of Pzz. Alternatively, inducing Bloch-like oscillations (in THz frequencies) cause ultra-high negative differential velocity without domain formation using an adequate temperature field. Moreover, we compare the Pzz of the FSWCNT to that of the superlattice (SL) (PzzSL), which shows that the Pzz of the FSWCNT is 8 orders of magnitude greater than that of the SL. It is worth noting that the large Pzz obtained and the ability to tune the FSWCNT to operate at high temperatures make the FSWCNT a potential candidate for thermoelectric applications.

Giant Thermoelectric Figure of Merit in Fluorine Doped Single Walled Carbon Nanotube

“…Practically, the phenomenon is used for electric power generation (Seebeck effect) or for cooling (Peltier effect) without mechanical moving parts [3][4][5]. The performance of a thermoelectric device is usually determined by its dimensionless figure-of-merit (FoM), ZT = α 2 σT /κ, where α, σ, T , κ are the Seebeck coefficient (thermoelectric power), the electrical conductivity, the absolute temperature, and the thermal conductivity (which comprises the electronic (κ e ) and the lattice (κ ) components), respectively [3][4][5][6][7][8][9]. Enhancements in the ZT have been achieved in nanostructures, mainly due to the thermal conductivity reduction by phonon-boundary scattering as the amount of interfaces increases [10].…”

“…Theoretical studies and experimental investigations of the thermoelectric properties of low dimensional (1−D and 2−D) systems have been pursued extensively for various materials [8,[11][12][13]. Quantum confinement of electrons are expected to lead to improved ZT value in low-dimensional materials, due to the anticipated enhancement of FoM parameters.…”

“…Quantum confinement of electrons are expected to lead to improved ZT value in low-dimensional materials, due to the anticipated enhancement of FoM parameters. 0−D structures hold even greater promise than 1−D and 2−D systems [8]. However, unlike 1−D and 2−D systems, where at least one of the directions is not confined and thus, can provide electrical conduction, 0−D structures such as quantum dots are confined in all directions and may pose difficulties for some applications [14][15][16].…”

“…The dominant contribution to the thermoelectric power is purely electronic, though in some materials, such as graphite, an electron-phonon scattering contribution or phonon drag effect also becomes prominent at certain temperature ranges, especially at low temperature. However, even though the thermal properties of nanotubes are dominated by phonons, we expect that the thermoelectric power will be primarily governed by the electronic drift contribution, the electronic band-structure of the nanotubes, and the electron scattering mechanisms [7][8][9]20]. SWCNTs skeletal structure enables the attachment of large number of foreign atoms to the surface without destroying the tubular structure.…”

“…SWCNTs skeletal structure enables the attachment of large number of foreign atoms to the surface without destroying the tubular structure. Doping an armchair-SWCNT with fluorine atoms changes its nature from metallic to semiconducting [8,[21][22][23][24][25].…”