High thermoelectric performance of tellurium-free n-type AgBi1-xSbxSe2 with stable cubic structure enabled by entropy engineering

Abstract AgBiSe2 is a promising n-type compound with high thermoelectric performance but suffers from a multiple structural phase transition. Here, we show the high-temperature rock salt phase can be stabilized at ambient conditions in AgBi1-xSbxSe2 solid solutions with x higher than 0.2, which is attributed to the increased configurational entropy. Moreover, the optimum increment of configurational entropy is determined by analyzing the weighted mobility and quality factor. Finally, benefiting from the intrinsically low lattice thermal conductivity and well-maintained carrier mobility, a peak zT value of 0.86 at 790 K, is attained for cubic AgBi0.8Sb0.2Se2 after bromine doping. This work highlights the importance of entropy engineering in thermoelectric performance and phase stability, providing insights into the discovery and design of environmental-friendly thermoelectrics.