Potential thermoelectric material Cs2[PdCl4]I2: a first-principles study

The electronic structures and thermoelectric properties of Cs-2[PdCl4]I-2 are investigated by first-principles calculations and semiclassical Boltzmann transport theory. Both electron and phonon transport are considered to attain the figure of merit ZT. A modified Becke-Johnson exchange potential, including spin-orbit coupling (SOC), is employed to investigate the electron part of Cs-2[PdCl4]I-2. It is found that SOC has an obvious effect on valence bands, producing huge spin-orbital splitting, which leads to a remarkable detrimental effect on the p-type power factor. However, SOC has negligible influence on conduction bands, so the n-type power factor hardly changes. The temperature dependence of lattice thermal conductivity by assuming an inverse temperature dependence is attained from a reported ultralow lattice thermal conductivity of 0.31 W m(-1)K(-1) at room temperature. Calculating scattering time tau is challenging, but a hypothetical t can be adopted to estimate thermoelectric conversion efficiency. The maximal figure of merit ZT is up to about 0.70 and 0.60 with scattering time tau = 10 (14) s and tau = 10 (15) s, respectively. These results convince us that Cs-2[PdCl4]I-2 may be an efficient thermoelectric material for real devices.