Nanostructured SnSe Integrated with Se Quantum Dot with Ultrahigh Power Factor and Thermoelectric Performance from Magnetic Field-Assisted Hydrothermal Synthesis

Thermoelectric materials which can directly convert thermal energy into electrical energy have great potential in solving energy crisis. SnSe emerges as one of the most intriguing new thermoelectric materials since the discovery of excellent thermoelectric properties in 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 dot. The critical nucleation energy reduces and the nucleation rate increases during hydrothermal synthesis process as high magnetic field is applied, which leads to presence of homogeneous distribution of Se quantum dots and smaller nano grains. Enhanced density of states and energy filtering effect contribute to a significant enhancement of Seebeck coefficient and power factor (PF) due to Se quantum dots and smaller nano grains. The enhanced density of states was directly identified by UPS measurements. With the aid of high magnetic field in solution chemistry, these materials maintain low thermal conductivity due to Se quantum dots, smaller nano grains and nanoprecipitates. Benefiting from the enhanced PF and reduced thermal conductivity, a high figure of merit (ZT) of ~ 2.0 at 873 K is achieved in Se quantum dot/Sn0.99Pb0.01Se nanocomposite. This work paves a new way for designing prospective thermoelectric materials by applying external high magnetic field.