Local resonance mechanism for enhancing the thermoelectric performance of PBCF-graphene nanoribbons

Phonon local resonance mechanism can effectively block phonon transport and thus reduce phonon thermal conductance. Inspired by this, we investigated the thermoelectric performance of Armchair-PBCF-graphene nanoribbons (A-PBCF-GNRs) and its branched structures by using non-equilibrium Green's function method. The results show that the thermoelectric performance of branched A-PBCF-GNRs can be significantly improved. Especially, the room-temperature ZT value of single branch A-PBCF-GNRs (SB-A-PBCF-GNRs) and double branch A-PBCF-GNRs (DB-A-PBCF-GNRs) can reach to 0.56 and 0.80, which is 1.5 and 2 times greater than that of A-PBCF-GNRs. Analysis shows that this is mainly attributed to the significant decrease in thermal conductance of branched A-PBCF-GNRs caused by the localized electronic and phonon states. Moreover, the mode resolved phonon transmission probabilities demonstrated that the local resonance mechanism of branched structure blocks the low-frequency acoustic phonon transmission. This work indicates the broad application prospects of the local resonance mechanism of branched structure in the thermoelectric field.