Enhanced Thermoelectric Performance of P-Type (Bi,Sb) 2 Te 3 by Incorporating Non-Stoichiometric Ag 5 Te 3 and Refining Te-Se Ratio.

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.