Nanostructured SnSe integrated with Se quantum dots with ultrahigh power factor and thermoelectric performance from magnetic field-assisted hydrothermal synthesis

Thermoelectric materials that can directly convert thermal energy into electrical energy have great potential in solving the present energy crisis. SnSe has emerged as one of the most intriguing new thermoelectric materials since the discovery of the excellent thermoelectric properties of its single crystals. Here, we develop a new solution synthesized method (in situ magnetic field-assisted hydrothermal synthesis) for achieving new nanostructured SnSe integrated with Se quantum dots. The critical nucleation energy reduces and the nucleation rate increases during the hydrothermal synthesis process as a high magnetic field is applied, which leads to the presence of the homogeneous distribution of Se quantum dots and smaller nano grains. Enhanced density of states and the energy filtering effect contribute towards a significant enhancement in the Seebeck coefficient and power factor (PF) due to the Se quantum dots and smaller nano grains. The enhanced density of states was directly identified by ultraviolet photoelectron spectroscopic measurements. With the aid of a high magnetic field in solution chemistry, these materials maintain low thermal conductivity due to the Se quantum dots, smaller nano grains and nanoprecipitates. Benefiting from the enhanced power factor and reduced thermal conductivity, a high figure of merit (ZT) of similar to 2.0 at 873 K was achieved in a Se quantum dot/Sn0.99Pb0.01Se nanocomposite. This work paves the way for the design of prospective thermoelectric materials by applying an external high magnetic field.