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Abstract Bismuth telluride alloys favor the applications of low‐grade waste heat recovery if their figure‐of‐merits are improved within the larger temperature range from 300 to 523 K. Herein, this work reports a synergistic optimization for Bi 0.5 Sb 1.5 Te 3 (BST) by incorporating the copper(II) phthalocyanine (CuPc), which is preferentially distributed at the grain boundary of BST after the spark plasma sintering process and suppresses the grain growth of BST. The lattice thermal conductivity of composites is then extensively reduced by the multiscale scattering induced by the CuPc. In addition, the Cu atoms diffuse into the lattice of BST and increase the whole concentration, thus suppressing the bipolar effect. As a result, the average zT value is effectively enhanced from 0.7 to 1.1 in the temperature range between 300 and 523 K. A high conversion efficiency of 6.8% is achieved in a single BST/CuPc 5 leg, which is 41.7% higher than that of BST at temperature different Δ T = 223 K. This result proves that the composition optimization of the BST/CuPc is a promising strategy to improve the application of BST‐based TE modules.
Wang et al. (Fri,) studied this question.