Ag deficiencies modulate electrical transport properties and optimize thermoelectric performance of AgSbSe₂

Besides excellent thermoelectric properties, composed of earth-abundant elements and featuring simple chemical compositions are more conducive to the practical fabrication and utilization of thermoelectric materials. In this study, a tellurium-free thermoelectric compound, AgSbSe₂, was synthesized, and the impact of Ag deficiencies on its thermoelectric performance was examined. It was found that the density of charge carriers of AgSbSe₂ can be effectively modulated by introducing slight Ag deficiencies, thereby significantly optimizing its electrical transport performance. A peak power factor of 6.63 μWcm⁻¹K⁻² @623 K is achieved in the sample with a composition of Ag_0.99SbSe₂, which is similar to the maximum value observed in Pb doped samples prepared by the same experimental production. Meanwhile, extremely low thermal conductivity was restrained in AgSbSe₂ with Ag deficiencies due to the effect of phonon scattering caused by crystal defects, which offsets the increased electrical thermal conductivity. Finally, a maximum zT value of 0.97 @623 K is obtained for Ag_0.99SbSe₂, which is comparable to that of heavily doped AgSbSe₂ with the conventional divalent cations doping at the Sb site.