Metal–insulator phase transition in TTT2I3 affected by iodine concentration

Abstract

It is found that the iodine content in the complex TTT2I3 may be varied from 1.5 to ≈ 1.55 atoms per molecule of TTT. Increasing of the iodine concentration in the complex gives rise to an increase in the degree of incommensurability of the TTT and the I sublattices and also the degree of disordering associated with losing the correlation in arrangement of different one‐dimensionally ordered iodine chains. It results in the change of conducting and magnetic properties of the complex. The temperature of the conductivity maximum moves down as the iodine concentration is increased in the complex, and the maximum is the higher, the lower its temperature. It is found that a phase transition of the metal‐insulator type exists in TTT2I3 with a transition temperature depending on the iodine content.

Thermoelectric Properties of Nanostructured Tetrathiotetracene Iodide Crystals: 3D Modeling

“…5  -1 m -1 [17]; 0.09 which corresponds to crystals grown from gaseous phase with stoichiometric conductivity 10 6  -1 m -1 [18]; 0.05 which corresponds to crystals grown from gaseous phase with somewhat higher conductivity 1.7×10…”

“…These results were obtained in strongly one-dimensional approximation, when the crystal is formed from 1D conductive molecular chains packed into a three-dimensional (3D) structure. In not very pure crystals of tetrathiotetracene-iodide, TTT 2 I 3 , grown from solution [17] with measured electrical conductivity σ xx = 1.810 5  -1 m -1 , Seebeck coefficient S xx = 39 μV/K and thermal conductivity  xx = 1.0 Wm -1 K -1 along conductive chains ZT  0.1 at room temperature was obtained. But in reported stoichiometric crystals [18], grown by gaseous phase method with σ xx = 10 6  -1 m -1 , a value of ZT ~ 1.4 is expected, if the hole concentration is diminished by two times [19].…”

Thin Film Organic Thermoelectric Generator Based on Tetrathiotetracene

“…At this point exact stoichiometry between TTT and iodine is expected to be TTT2I3, which according to literature has the best thermoelectric efficiency. [34,44] The sample was made by reactive deposition but it is similar to samples made by post-deposition iodine TTT doping where 0.46 μWm -1 K -2 and 121 S m -1 respectively were realized.…”

Metal-Insulator Transition of Peierls Type in Quasi-One-Dimensional Crystals of TTT<sub>2</sub>I<sub>3</sub>

“…Quasi-one-dimensional (Q1D) organic crystals of tetrathiotetracene-iodide, TTT 2 I 3 , were synthesized independently and nearly simultaneously [1] [2] [3] [4] with the aim to find superconductivity in a low dimensional conductor. However, these crystals with rather high electrical conductivity near room temperature, at low temperature showed a transition into a dielectric state.…”

“…The electrons on iodine ions are in a rather localized states and do not participate in the transport. In the crystals grown by sublimation of TTT and iodine in an inert gas flow [3] the room electrical conductivity σ along b direction achieves (10 3 -10 4 ) Ω −1 •cm −1 , but in those grown from solution [1] [2] σ ~ (800 -10 3 ) Ω −1 •cm −1 . Such variation in σ of crystals, grown in different laboratories, shows that the conductivity properties of TTT stacks are highly sensitive to defects and impurities.…”