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.