Effect of the 2D phonon spectrum on the electric conductivity and thermopower of tetrathiotetracene iodide crystals

Abstract

Thermoelectric transport along the molecular chains of quasi-one-dimensional organic crystals of tetrathiotetracene iodide, TTT2I3, is studied in terms of a quasi-two dimensional (2D) model applying the linearized Boltzmann kinetic equation. Earlier, for simplicity, we have considered the lattice vibrations in a 1D approximation. In this paper, the full 2D spectrum for acoustic longitudinal phonons is taken into account and the effect of this consideration on the electric conductivity and thermopower (Seebeck coefficient) is studied. Numerical results and comparison with previous calculations are presented. It is shown that, if the 2D phonon spectrum is taken instead of the 1D one, the electric conductivity slightly increases and the thermopower decreases, although insignificantly.