Thermoelectric Properties of Nanostructured Tetrathiotetracene Iodide Crystals: 3D Modeling

Abstract

A more complete three dimensional (3D) physical model for nanostructured crystals of tetrathiotetracene iodide, TTT2I3, is presented. The restrictions on the thermoelectric figure of merit ZT that this model involves are determined. Atthe same time the criteria of application of simplified 1D model are defined more precisely. In TTT2I3 crystals the carriers are holes. As earlier, two interaction mechanisms of holes with acoustic phonons are considered, generalized for 3D case. One interaction is similar to that of polaron and other to that of deformation potential. Interaction of carriers with impurities and defects is also taken into account. Along chains (x direction) the transport mechanism is of the band type, but in the transversal directions it is of hopping type. The electrical conductivity σxx,thethermopower (Seebeck coefficient) Sxx, the electronic thermal conductivity and (ZT)xx along the conductive chains have been modelled for the first time in the 3D model. Optimal parameters which predict a considerable increase of (ZT)xx are determined.