Thermoelectric properties of tetrahedrally bonded wide-gap stannite compounds ${\text{Cu}}_2{\text{ZnSn}}_{1-x}{\text{In}}_x{\text{Se}}_4$

It is usually accepted that good thermoelectric (TE) materials should be narrow-gap semiconductors. Here we show an example that the tetrahedrally bonded stannite compound ${\text{Cu}}_2{\text{ZnSnSe}}_4$ with a band gap of 1.44 eV can also exhibit a high figure of merit at intermediate temperature. The highly distorted structure strives for the relatively low thermal conductivity, and the tunability of the electrical properties were demonstrated through doping. The maximum $ZT$ of ${\text{Cu}}_2{\text{ZnSn}}_{0.90}{\text{In}}_{0.10}{\text{Se}}_4$ reaches 0.95 at 850 K. This work may open a way for exploring high-performance TE materials with the family of widely existing tetrahedrally bonded semiconductors.