Interface design of the thermoelectric transport properties of phosphorene-tetrathiafulvalene nanoscale devices

Interface design and energy band engineering are two key strategies for improving the thermoelectric conversion efficiency of low dimensional nanoscale devices. By using first-principle-based density functional theory combined with a non-equilibrium Green function method, the thermoelectric properties of a single tetrathiafulvalene (TTF) molecule coupled with armchair phosphorene nanoribbons (APNRs) within different interface modes have been investigated. The results indicate that phonon transport can be dramatically suppressed in this intermediate weak-coupling system due to strong interfacial phonon scattering behavior, where very few phonons can propagate through two nonbonded interface regions from left side lead to a TTF molecule and then to right side lead. Furthermore, connecting a thiophene group at both the head and tail of the intermediate TTF molecule can significantly enhance the power factor (S2 sigma) of such a weak-coupling system based on an out-of-plane electronic transmission mechanism, and there is obvious charge transfer from S atoms to upper and lower APNRs. Compared to a single regular method, composite interface co-design can achieve more accurate control of thermal/electrical transmission performance. Electrical conductance can be effectively improved with low phonon thermal conductance being maintained at the same time, and an excellent thermoelectric figure of merit (ZT) of 0.73 has been obtained near 0.6 eV. S atoms can facilitate the out-of-plane electronic transport of TTF molecules.

Automated summary

Interface design and energy band engineering are key strategies for improving the thermoelectric conversion efficiency of low dimensional nanoscale devices. In this study, the thermoelectric properties of a TTF molecule coupled with APNRs were investigated using theoretical and simulation methods. It was found that phonon transport can be suppressed in the weak-coupling system and the power factor can be enhanced by connecting thiophene groups.