A Recipe for a Great Meal: A Benchtop Route from Elemental Se to Superior Thermoelectric β-Ag₂Se

The low-temperature modification of β-Ag₂Se has proven to be useful as a near-room-temperature thermoelectric material. Over the past years, research has been devoted to interstitial, vacancy, and substitutional doping into the parent β-Ag₂Se structure, aiming at tuning the material's charge and heat transport properties to enhance thermoelectric performance. The transformation of β-Ag₂Se into α-Ag₂Se at ∼134 °C and the low solubility of dopants are the main obstacles for the doping approach. Herein, we report a facile, safe, scalable, and cost-effective benchtop approach to successfully produce metal-doped β-Ag₂Se. The doped materials display a remarkable enhancement of thermoelectric performance with a record-high peak zT of 1.30 at 120 °C and an average zT of ∼1.15 in the 25-120 °C range for 0.2 at. % Zn-doped Ag₂Se. The enhancement in zT is attributed to point defects created by Zn doping into Ag vacancies/interstitials, which enhances the scattering of phonons and tunes the charge carrier properties, leading to the significant suppression of thermal conductivity. The simplicity of the synthetic method developed herein and the high performance of the final products provide an avenue to produce high-quality Ag₂Se-based thermoelectric materials.