Liquid-Phase Manipulation Securing Enhanced Thermoelectric Performance of Ag₂Se

Developing n-type materials with high peak and/or average ZT (ZT is the figure of merit) is an urgent need for the lower ZT of the existing n-type BiTeSe materials compared with the p-type BiSbTe materials. Here, we demonstrate that liquid-phase sintering can lead to lowered thermal conductivity and an improved power factor in n-type Ag₂Se, which originates from the greatly lowered electronic thermal conductivity attributed to the decreased mobility and improved Seebeck coefficients because of increased effective mass. Benefiting from this, the maximum ZT (ZT_max) of ∼1.21 and the average ZT (ZT_ave) of 1.06 are successfully achieved in polycrystalline Ag₂Se. In this work, ZT_ave is the highest reported value, being 26% larger than that of Ag₂Se reported. Our work shows that liquid-phase sintering to achieve improved thermoelectric (TE) performance opens a great opportunity for designing prospective thermoelectrics.