High Performance Thermoelectric Power of Bi 0.5 Sb 1.5 Te 3 Through Synergistic Cu 2 GeSe 3 and Se Incorporations.

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 ΔT = 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.