Enhanced Thermoelectric Performance of P‐Type (Bi,Sb)2Te3 by Incorporating Non‐Stoichiometric Ag5Te3 and Refining Te‐Se Ratio

Abstract Power generation modules utilizing thermoelectric (TE) materials are suitable for recycling widespread low‐grade waste heat (<600 K), highlighting the immediate necessity for advanced Bi 2 Te 3 ‐based alloys. Herein, the substantial enhancement in TE performance of the p ‐type Bi 0.4 Sb 1.6 Te 3 (BST) sintered sample is realized by subtly incorporating the non‐stoichiometric Ag 5 Te 3 and counteractive Se. Specifically, Ag atoms diffused into the BST lattice improve the density‐of‐states effective mass ( m d * ) and boost the hole concentration for the suppressed bipolar effect. The addition of Se further improves m d * prompting the room‐temperature power factor upgrade to 46 W cm −1 K −2 . Concurrently, the lattice thermal conductivity is considerably lowered by multiple scattering sources exemplified by Sb‐rich nanoprecipitates and dense dislocations. These synergistic results yield a high peak ZT of 1.44 at 375 K and an average ZT of 1.28 between 300 and 500 K in the Bi 0.4 Sb 1.6 Te 2.95 Se 0.05 + 0.05 wt.% Ag 5 Te 3 sample. More significantly, when coupled with n ‐type zone‐melted Bi 2 Te 2.7 Se 0.3 , the integrated 17‐pair TE module achieves a competitive conversion efficiency of 6.1% and an output power density of 0.40 W cm −2 at a temperature difference of 200 K, demonstrating great potential for practical applications.