Ag Interstitial Inhibition and Phonon Scattering at the ZnSe Nano-Precipitates to Enhance the Thermoelectric Performance of Ag2Se

Ag2Se-based thermoelectric (TE) materials have attracted significant attention recently due to their potential application near room temperature. Manipulating the stoichiometric ratio of Ag/Se and anion doping are usually used as effective approaches to enhance the TE properties. Here, we report a strategy to simultaneously enhance the power factor (PF) and reduce the thermal conductivity of Ag2Se by introducing ZnSe nano-precipitates. The excessive carrier concentration in the intrinsic Ag2Se is successfully reduced by the Ag interstitial inhibition due to the introduction of secondary-phase ZnSe nano-precipitates, thereby enhancing the PF up to a maximum value of ∼22.2 μW m–1 K–2 at 383 K and decreasing the electronic thermal conductivity from ∼1.2 to ∼0.8 W m–1 K–1 at 383 K. In addition, the phonon scattering at ZnSe nano-precipitates contributes to the reduction of lattice thermal conductivity from ∼0.5 to ∼0.4 W m–1 K–1 at 383 K. As a result, a high peak zT of ∼0.7 at 383 K and an average zT of 0.6 at 313–383 K are obtained in the sample Ag2Se-0.005ZnSe, which is one of the highest values amongst Ag2Se-based TE materials. This study could provide guidance to improve the TE properties of materials similar to Ag2Se.