Thermoelectric transport properties of S-doped In_0.9Si_0.1Se

Layered metal chalcogenides with highly promising thermoelectric properties have attracted attention owing to their intrinsically low thermal conductivity, which originates from their unique layered structure and van der Waals bonding. InSe, a post-transition metal chalcogenide, also has layered atomic structure and low thermal conductivity. We investigate the effects of S doping of Si-doped InSe, In_0.9Si_0.1Se. The S-doped In_0.9Si_0.1Se exhibits enhanced thermoelectric properties, with a higher power factor and lower thermal conductivity compared to Si-doped InSe. A significant increase in carrier mobility has an overall positive effect on the electronic transport properties, resulting in a systematic increase in power factor from 0.05 to 0.15 mW/mK² with S doping. In addition, the thermal conductivity systematically decreases with S doping owing to additional point-defect scattering. Because of the higher power factor and lower thermal conductivity, the thermoelectric figure of merit of the In_0.9Si_0.1Se_0.9S_0.1 sample at 735 K was 0.18, which is 3.6 times that of In_0.9Si_0.1Se.