High-Performance Thermoelectric Energy Conversion: A Tale of Atomic Ordering in AgSbTe2

The highly enhanced thermoelectric figure of merit, zT approximate to 2.6 at 573 K, obtained recently in Cd-doped polycrystalline AgSbTe2 by Roychowdhury et al. (Science 2021, 371, 722) brings it to the forefront of thermoelectric and energy materials research. Ag/Sb cationic ordering in polycrystalline AgSbTe2 was a challenging issue for a long time: their ordered arrangement in the cationic sublattice in polycrystalline samples remained elusive despite multiple theoretical predictions and experimental studies. Recently, selective cation doping has been used to enhance the Ag/Sb ordering, and cation ordered nanoscale (2-4 nm) domains were observed in polycrystalline AgSbTe2, which reduce lattice thermal conductivity. The enhanced cation ordering also delocalizes disorder-induced localized electronic states, and consequently the electronic transport enhances. In this Focus Review, we provide the details of the rational design of a high-performance thermoelectric material using the recently developed atomic order-disorder optimization strategy with AgSbTe2 as an example. Atomic disorder is ubiquitous in most thermoelectric materials, and the atomic order-disorder optimization strategy applies to a large variety of thermoelectric materials.