Theoretical analysis of the thermoelectric properties of penta-PdX2 (X = Se, Te) monolayer

Based on the successful fabrication of PdSe 2 monolayers, the electronic and thermoelectric properties of pentagonal PdX 2 (X = Se, Te) monolayers were investigated via first-principles calculations and the Boltzmann transport theory. The results showed that the PdX 2 monolayer exhibits an indirect bandgap at the Perdew–Burke–Ernzerhof level, as well as electronic and thermoelectric anisotropy in the transmission directions. In the PdTe 2 monolayer, P-doping owing to weak electron–phonon coupling is the main reason for the excellent electronic properties of the material. The low phonon velocity and short phonon lifetime decreased the thermal conductivity ( κ l ) of penta-PdTe 2 . In particular, the thermal conductivity of PdTe 2 along the x and y transmission directions was 0.41 and 0.83 Wm −1 K −1 , respectively. Owing to the anisotropy of κ l and electronic structures along the transmission direction of PdX 2 , an anisotropic thermoelectric quality factor ZT appeared in PdX 2 . The excellent electronic properties and low lattice thermal conductivity ( κ l ) achieved a high ZT of the penta-PdTe 2 monolayer, whereas the maximum ZT of the p- and n-type PdTe 2 reached 6.6 and 4.4, respectively. Thus, the results indicate PdTe 2 as a promising thermoelectric candidate.