Facile and scalable strategy for fabricating dense bulk Ag2Se as a high-performance thermoelectric material

Abstract

Silver selenide (Ag2Se) is a promising n-type thermoelectric material because of its excellent thermoelectric performance near room temperature, but conventional methods for fabricating bulk Ag2Se require high temperatures and pressures making scalable production a challenge. Here, a facile and scalable strategy is presented for fabricating high-performance dense Ag2Se1.2 thermoelectric material by incorporating excess Se in solution-processed Ag2Se powders. The excess Se facilitates liquid-phase-assisted grain growth during annealing at 623 K under ambient pressure, which greatly improves microstructural properties such as the grain connectivity and bulk density. In experiments, Ag2Se1.2 exhibited a high-power factor and reduced lattice thermal conductivity leading to a maximum figure of merit of 0.927 at 393 K. The shape-conformable nature of Ag2Se1.2 also allows for the fabrication of cylindrical thermoelectric generators with a stable output voltage and power at various temperature differences. This strategy is a highly effective approach for improving not only the thermoelectric and mechanical performances of Ag2Se but also its applicability in curved or flexible energy harvesting devices.