Lead-free GeTe alloys with high thermoelectric performance for low-grade waste heat energy harvesting
Haiqi Li, Chen Chen, Jinxuan Cheng, Yuanhang Xia, Shuang Lyu, Kejia Liu, Wenhua Xue, Dongyi Shen, Wenxuan Wang, Qian Zhang, Yue Chen
Abstract
Harvesting and utilization of low-grade waste heat dissipated from industries have garnered immense attention in recent years. Thermoelectric materials, which can directly convert heat into electricity, provide an eco-friendly solution for waste heat recovery. Recently, GeTe-based materials have developed as strong competitors to Bi 2 Te 3 near room temperature. Nonetheless, despite exhibiting comparable thermoelectric performance, the majority of these GeTe alloys incorporate toxic Pb, thus limiting the practical application. Herein, a boosted zT was achieved in Ge 0.93 Bi 0.05 Te over the entire temperature range by introducing Ge deficiency. Further AgSbTe 2 alloying leads to a remarkable increase in density-of-states effective mass and high weighted mobility. Thermally, the addition of AgSbTe 2 forms various phonon scattering centers including domain structures, dislocations, and phase boundaries, contributing to the low lattice thermal conductivity. As a result, a high average zT of 1.34 (323–573 K) is obtained in the lead-free (Ge 0.93 Bi 0.05 Te) 85 (AgSbTe 2 ) 15 material, and its maximum single-leg conversion efficiency reaches 8.6 % at Δ T = 273 K. The outstanding thermoelectric performance and the lead-free characteristic presented in our study shed light on the potential of GeTe alloys for applications in recovering low-grade waste heat. • A high average zT of 1.34 (323–573 K) in the lead-free GeTe material. • The maximum single-leg conversion efficiency reaches 8.6 % at Δ T = 273 K. • Ge deficiency and AgSbTe 2 alloying enhance the carrier effective mass, resulting in excellent weighted mobility. • The introduction of multiscale hierarchical defects strongly blocks phonon transport.