High Performance Thermoelectric Power of Bi_0.5Sb_1.5Te₃Through Synergistic Cu₂GeSe₃and Se Incorporations

Abstract

Abstract Bi 2 Te 3 ‐based alloys are the benchmark for commercial thermoelectric (TE) materials, the widespread demand for low‐grade waste heat recovery and solid‐state refrigeration makes it imperative to enhance the figure‐of‐merits. In this study, high‐performance Bi 0.5 Sb 1.5 Te 3 (BST) is realized by incorporating Cu 2 GeSe 3 and Se. Concretely, the diffusion of Cu and Ge atoms optimizes the hole concentration and raises the density‐of‐states effective mass ( m d * ), compensating for the loss of “donor‐like effect” exacerbated by ball milling. The subsequent Se addition further increases m d * , enabling a total 28% improvement of room‐temperature power factor ( S 2 σ ), reaching 43.6 µW cm −1 K −2 compared to the matrix. Simultaneously, the lattice thermal conductivity is also significantly suppressed by multiscale scattering sources represented by Cu‐rich nanoparticles and dislocation arrays. The synergistic effects yield a peak ZT of 1.41 at 350 K and an average ZT of 1.23 (300–500 K) in the Bi 0.5 Sb 1.5 Te 2.94 Se 0.06 + 0.11 wt.% Cu 2 GeSe 3 sample. More importantly, the integrated 17‐pair TE module achieves a conversion efficiency of 6.4%, 80% higher than the commercial one at Δ T = 200 K. These results validate that the facile composition optimization of the BST/Cu 2 GeSe 3 /Se is a promising strategy to improve the application of BST‐based TE modules.