First-Principles Investigation on the Significant Anisotropic Thermoelectric Transport Performance of a Hf2Cl4 Monolayer

Recently, a series of novel thermoelectric (TE) materials have been rapidly screened out through high-throughput calculation; meanwhile, although this method improves the screening speed, it also reduces the accuracy of estimation. Therefore, further accurate analysis of the newly reported materials’ electrical and thermal transport properties should be conducted to understand their microscopic transport mechanism. In this work, we investigate the TE transport properties of monolayer Hf 2 Cl 4 in which it has been figured out that there exists a high electronic fitness function (EFF) value for TE applications based on the first-principles approach by using density functional theory and the semi-classical Boltzmann transport equation. The TE parameters of monolayer Hf 2 Cl 4, including thermal conductivity, Seebeck coefficient, electrical conductivity, and so on, are calculated to evaluate its figure of merit ZT at temperatures of 300, 500, and 700 K. It is found that these TE parameters are highly anisotropic between x - and y -directions, which is the critical factor for its excellent TE performance. The optimal figure of merit of 3.2 is achieved along the x -direction for hole doping at 700 K. Our study reveals that monolayer Hf 2 Cl 4 could be a suitable candidate for TE materials, and high-throughput calculation screening is effective for enhancing TE performance.