A wide-band-gap $p$-type thermoelectric material based on quaternary chalcogenides of ${\text{Cu}}_2\text{ZnSn}{Q}_4$ $\left(Q=\text{S},\text{Se}\right)$

Chalcopyritelike quaternary chalcogenides, ${\text{Cu}}_2\text{ZnSn}{Q}_4$ $\left(Q=\text{S},\text{Se}\right)$, were investigated as an alternative class of wide-band-gap $p$-type thermoelectric materials. Their distorted diamondlike structure and quaternary compositions are beneficial to lowering lattice thermal conductivities. Meanwhile, partial substitution of Cu for Zn creates more charge carriers and conducting pathways via the $\text{Cu}{Q}_4$ network, enhancing electrical conductivity. The power factor and the figure of merit $\left(ZT\right)$ increase with the temperature, making these materials suitable for high temperature applications. For ${\text{Cu}}_{2.1}{\text{Zn}}_{0.9}\text{Sn}{Q}_4$, $ZT$ reaches about 0.4 at 700 K, rising to 0.9 at 860 K.