Enhanced High-Temperature Thermoelectric Performance by Strain Engineering in BiOCl

Semiconductor BiOCl has a layered structure with ultralow lattice thermal conductivity [Q.D. Gibson et al., Science 373, 1017--1022 (2021)] and has potential applications in the field of thermoelectric materials. In the present study, the thermoelectric properties of BiOCl crystals are accurately predicted using the first-principles calculation combined with Boltzmann transport theory. The dimensionless figure of merit ($ZT$) of $p$-type BiOCl is found to be 0.2 at room temperature, reaching 1.1 at 800 K. In addition, applying in-plane biaxial tensile strain ${ϵ}_{xy}$ can lead to a further increase in the value of $ZT$ to 1.9 at 800 K. This means that $p$ BiOCl is an excellent high-temperature thermoelectric material. And this is due to the fact that biaxial strain drastically reduces the lattice thermal conductivity and the shift of the valence band toward the Fermi level can optimize the carrier concentration. Thus, the present work paves a way for the design of adjustable high-temperature thermoelectric materials.