Thermoelectric Transport Properties of Cairo Pentagonal AlPTe and GaPTe Monolayers

Pentagonal monolayers have attracted high research interest owing to their exotic lattice characteristics originating from the unique Cairo pentagonal tiling topology. In this article, pentagonal AlPTe and GaPTe monolayers are investigated for their thermoelectric properties. Density functional theory was employed with pure quadratic corrections to enforce the rotational invariance conditions for phonon transport. The effects of acoustic phonon scattering, impurity scattering, and polarized phonon scattering factors were also considered for the electronic transport calculations. The results find that the small group velocity combined with strong phonon scattering leads to the low lattice thermal conductivity of 0.6 W/mK. Moreover, the degenerate top valence bands lead to high electrical conductivity and, thereby, high thermal power factors in these pentagonal monolayers. Specifically, a high ZT value of 3.5 at 500 K can be achieved by the p-type GaPTe monolayer. A high thermoelectric conversion efficiency of up to ∼28% makes these pentagonal monolayers promising candidates for thermoelectric applications at the nanoscale.