High Thermoelectric Performance in Phonon-Glass Electron-Crystal Like AgSbTe 2 .

Achieving glass-like ultra-low thermal conductivity in crystalline solids with high electrical conductivity, a crucial requirement for high-performance thermoelectric energy conversion, continues to be a formidable challenge. A careful balance between electrical and thermal transport is essential for optimizing the thermoelectric performance of a material. Despite this inherent trade-off, the experimental realization of an ideal thermoelectric material with a "phonon-glass electron-crystal" (PGEC) nature has rarely been achieved. Here, we have demonstrated PGEC-like AgSbTe 2 by tuning the atomic disorder upon Yb doping, which resulted in an outstanding thermoelectric performance with figure of merit, zT∼2.4 at 573 K. Yb-doping induced enhanced atomic ordering decreases the overlap between the hole and phonon mean free paths and consequently leads to a PGEC-like transport behaviour in AgSbTe 2 . We observed a two-fold increase in electrical mobility while keeping the position of the Fermi level (E F ) nearly unchanged, which significantly increased the electrical conductivity and corroborates the enhanced crystalline nature of the AgSbTe 2 lattice upon Yb doping for electrical transport. The cation-ordered domains, on the other hand, lead to the formation of nanoscale superstructures (∼ 2 to 4 nm) that strongly scatter heat carrying phonons, resulting in a temperature-independent glass-like thermal conductivity. Furthermore, we have achieved a promising output power density of 388 mWcm -2 in a 4-leg device fabricated using 4 mol% Yb-doped AgSbTe 2 as the p-type analogue. Our strategy paves the way for realizing high thermoelectric performance in various disordered crystals by making them amorphous to phonons while favoring crystal-like electrical transport. This article is protected by copyright. All rights reserved.