Enhancing the thermoelectric performance of SnSe_1-xTe_x nanoplates through band engineering

We developed a facile microwave-assisted solvothermal method to produce large-scale SnSe_1-xTe_x nanoplates with tens of microns in length and several hundred nanometers in thickness. Enhancements in both peak figure-of-merit (1.1) at 800 K and average figure-of-merit (0.56) from 300 to 800 K were achieved in the p-type SnSe_0.9Te_0.1 pellet. In addition to the decreased thermal conductivity, the enhancement in figure-of-merit was mainly due to the increase in the power-factor over the mid-temperature range. The enhanced power-factor is caused by the high preferential orientation, large carrier concentration, and the band convergence of multiplevalences. The as-synthesized two-dimensional SnSe_1-xTe_x structures with a large size ratio between the lateral and axial directions secure high preferential orientation in the correspondingly sintered pellet, and the produced Sn vacancies increase the carrier concentration. Based on the optical properties and density functional calculations, we examined the band structure evolution of SnSe_1-xTe_x with increasing Te ratio to confirm the band convergence. This study of alloying with Te provides an alternative approach to enhance the thermoelectric performance of SnSe.