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

Abstract

AbstractPower generation modules utilizing thermoelectric (TE) materials are suitable for recycling widespread low‐grade waste heat (<600 K), highlighting the immediate necessity for advanced Bi2Te3‐based alloys. Herein, the substantial enhancement in TE performance of the p‐type Bi0.4Sb1.6Te3 (BST) sintered sample is realized by subtly incorporating the non‐stoichiometric Ag5Te3 and counteractive Se. Specifically, Ag atoms diffused into the BST lattice improve the density‐of‐states effective mass (md*) and boost the hole concentration for the suppressed bipolar effect. The addition of Se further improves md* 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 Bi0.4Sb1.6Te2.95Se0.05 + 0.05 wt.% Ag5Te3 sample. More significantly, when coupled with n‐type zone‐melted Bi2Te2.7Se0.3, 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.