Engineering of Thermoelectric Composites Based on Silver Selenide in Aqueous Solution and Ambient Temperature.

The direct, solid state, and reversible conversion between heat and electricity using thermoelectric devices finds numerous potential uses, especially around room temperature. However, the relatively high material processing cost limits their real applications. Silver selenide (AgSe) is one of the very few n-type thermoelectric (TE) materials for room-temperature applications. Herein, we report a room temperature, fast, and aqueous-phase synthesis approach to produce AgSe, which can be extended to other metal chalcogenides. These materials reach TE figures of merit () of up to 0.76 at 380 K. To improve these values, bismuth sulfide (BiS) particles also prepared in an aqueous solution are incorporated into the AgSe matrix. In this way, a series of AgSe/BiS composites with BiS wt % of 0.5, 1.0, and 1.5 are prepared by solution blending and hot-press sintering. The presence of BiS significantly improves the Seebeck coefficient and power factor while at the same time decreasing the thermal conductivity with no apparent drop in electrical conductivity. Thus, a maximum value of 0.96 is achieved in the composites with 1.0 wt % BiS at 370 K. Furthermore, a high average value () of 0.93 in the 300-390 K range is demonstrated.