Molecular junctions are promising candidates for thermoelectric devices due to the potential to tune the electronic and thermal transport properties. However, a high figure of merit is hard to achieve, without reducing the phononic contribution to thermal conductance. Here, we propose a strategy to suppress phonon transport in graphene-based molecular junctions preserving high electronic power factor, using nonbonded pi-stackal systems. Using first-principles calculations, we find that the thermal conductance of pi-stacked systems can be reduced by about 95%, compared with that of a covalently bonded molecular junction. Phonon transmission of pi-stacked systems is largely attenuated in the whole frequency range, and the remaining transmission occurs mainly below 5 THz, where out-of-plane channels dominate. The figure of merit (ZT) of the pi-stacked molecular junction is dramatically enhanced because of the very low phononic thermal conductance, leaving tom for further optimization of the electronic properties.
Li, Q., Strange, M., Duchemin, I., Donadio, D., & Solomon, G. C. (2017). A Strategy to Suppress Phonon Transport in Molecular Junctions Using pi-Stacked Systems. Journal of Physical Chemistry C, 121(13), 7175-7182. https://doi.org/10.1021/acs.jpcc.7b02005