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

Based on the successful fabrication of PdSe monolayers, the electronic and thermoelectric properties of pentagonal PdX (X = Se, Te) monolayers were investigated first-principles calculations and the Boltzmann transport theory. The results showed that the PdX 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 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 ( ) of penta-PdTe. In particular, the thermal conductivity of PdTe along the x and y transmission directions was 0.41 and 0.83 WmK, respectively. Owing to the anisotropy of and electronic structures along the transmission direction of PdX, an anisotropic thermoelectric quality factor appeared in PdX. The excellent electronic properties and low lattice thermal conductivity ( ) achieved a high of the penta-PdTe monolayer, whereas the maximum of the p- and n-type PdTe reached 6.6 and 4.4, respectively. Thus, the results indicate PdTe as a promising thermoelectric candidate.