Realizing High Wide-Temperature-Range Thermoelectric Performance in Ga, I, and S co-doped AgSbTe₂

Herein, a peak ZT value of ≈2 at 625 K and an average ZT of 1.46 are achieved in the AgSbTe₂ system through band engineering and multiscale phonon scattering. This demonstrates that Ga doping achieves band convergence and an additional impurity level between the valence and conduction bands. In contrast, I and S doping contribute profound band flattening. The collective effect of band engineering yields an improved Seebeck coefficient (S) and power factor (PF). The band manipulation strategy facilitated the attainment of peak PF of 17.9 µW cm^-1 K^-2 at 625 K, and an excellent average power factor (PF_ave) of 15.12 µW cm^-1 K^-2 is achieved for AgSb_0.97Ga_0.03Te_1.76S_0.15I_0.09 sample. In the meanwhile, the combined presence of coherent and incoherent nanoprecipitates introduces strong phonon scattering in AgSbTe₂ matrix, leading to a significantly suppressed lattice thermal conductivity. The lowest lattice thermal conductivity as low as 0.31 W m^-1K^-1 is achieved in AgSb_0.98Ga_0.02Te_1.84S_0.10I_0.06 sample. The vast increase of peak ZT and average ZT promotes AgSbTe₂ as a promising candidate for widespread applications for waste heat recovery and power generation near room-temperature range (300-625 K).