Thermoelectric Properties Regulated by Quantum Size Effects in Quasi-One-Dimensional γ-Graphdiyne Nanoribbons

Using density functional theory combined with the first principles calculation method of non-equilibrium Green's function (NEGF-DFT), we studied the thermoelectric (TE) characteristics of one-dimensional gamma-graphdiyne nanoribbons (gamma-GDYNRs). The study found that the thermal conductivity of gamma-GDYNRs has obvious anisotropy. At the same temperature and geometrical size, the lattice thermal conductivity of zigzag-edged gamma-graphdiyne nanoribbons (gamma-ZGDYNRs) is much lower than that of armchair-edged gamma-graphdiyne nanoribbons (gamma-AGDYNRs). We disclose the underlying mechanism for this intrinsic orientation. That is, gamma-AGDYNRs have more phonon dispersion over the entire frequency range. Furthermore, the orientation dependence increases when the width of the gamma-GDYNRs decreases. These excellent TE properties allow armchair-edged gamma-graphdiyne nanoribbons with a planar width of 1.639 nm (gamma-Z(2)GDYNRs) to have a higher power factor and lower thermal conductivity, ultimately resulting in a significantly higher TE conversion rate than other gamma-GDYNR structures.