Supercompliant Lattice Boosts n‐type AgSbTe2 Thermoelectrics

Abstract AgSbTe 2 ‐based compounds, the most promising near‐room‐temperature thermoelectric material, so far fail to deliver n‐type performance neither theoretically nor experimentally. Its intrinsic electron‐killer defects with very low formation energy prevent conventional n‐type doping. Herein, the first n‐type AgSbTe 2 by building a supercompliant lattice, which is extremely soft with an n‐type doping efficiency far beyond the Hume–Rothery rule settled phase boundary, is reported. The overdosed supercompliant lattice gives Young's modulus lower than the 2D van der Waals crystals, globally softening the phonons. This results in a minimal sound velocity of 1950 m·s −1 , which lies far below all AgSbTe 2 ‐based compounds previously reported. The substantially softened phonons lead to a low κ of 0.27 W·m −1 ·K −1 that approaches the theoretical minimum. Accordingly, the n‐type Ag 0.8 Na 0.3 Sb 0.6 Bi 0.4 Te 2 demonstrates a ZT value of ≈0.45 at the near‐room‐temperature range, which is the highest n‐type performance ever reported. This work unlocks the door for AgSbTe 2 as an exceptional n‐type thermoelectric material.