High-performance thermoelectric energy conversion: A tale of atomic ordering in AgSbTe2

The highly enhanced thermoelectric figure of merit, zT ≈ 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.