Improving the thermoelectric performance of the SnS monolayer by Na doping: A theoretical study

Aiming at exploring new thermoelectric (TE) materials of high performance, we theoretically calculate the TE transport properties including the Seebeck coefficient, electrical conductance, thermal conductance, power factor, and figure of merit ZT of the SnS monolayer. Different from the heavy-metal doping, the economical and environment-friendly Na doping is adopted to improve the ZT of the monolayer SnS. It is shown that the Na doping can increase the maximum ZT along the armchair and zigzag directions, respectively, and the highest ZT peak is moved to the proximity of chemical potential μ=0eV, which indicates that the corresponding TE device can work at a low bias voltage. As the temperature increases from 300 K to 800 K, the maximum ZT of the pristine SnS monolayer is increased from 0.89 to 2.26 (from 1.33 to 2.89) along the armchair (zigzag) direction, and the maximum ZT of the Na-doped one is increased from 1.24 to 2.45 (from 1.44 to 2.86) along the armchair (zigzag) direction. This implies that the Na-doped SnS monolayer can be utilized to design promising TE devices working in a broad temperature scope and at a lower bias voltage.