Ag-Nanoinclusion-Induced Enhanced Thermoelectric Properties of Ag2S

The effects of Ag nanoinclusions on thermoelectric properties of Ag2S semiconducting nanostructures, synthesized by a novel one-pot facile polyol method, have been investigated. The resulting products are characterized by powder XRD, EDAX, XPS, and UV-vis techniques. FESEM images reveal the formation of disc-shaped Ag2S nanoparticles with an average thickness of 52 nm and diameters ranging from 50 nm to a few hundreds of nm. All samples show a systematic reduction in electrical resistivity with increasing Ag content in the composites. The Seebeck coefficient (alpha) values for the Ag nanoparticle-incorporated Ag2S nanocomposites are notably high near 300 K because of the low-energy charge-carrier filtering effect, which is due to preferential scattering of low-energy electrons at the barrier potentials set up at metal-semiconductor interfaces. The theoretical fitting of alpha data reveals a systematic shift of the Fermi level toward the conduction band edge with increasing Ag content in the composites. A significantly improved thermoelectric power factor at 325 K is observed for a wide range of Ag nanoinclusions with the highest ZT of 0.0029 at 325 K in the Ag2S-Ag nanocomposite with 20.1% Ag.