Efficient stepwise carrier concentration optimization in Ge(1+x)−ySbyTe

Abstract

Owing to superior thermoelectric properties, GeTe shows practical applications in power generation and refrigeration. However, the high carrier concentration limits its high performance. Here, a stepwise design, called Ge-vacancy suppression and Sb-doping of Ge_(1+x)−ySb_yTe, has been developed to optimize the carrier concentration. Considering that the extra Ge restricts the formation of Ge vacancies to reduce the carrier concentration and over-excessive Ge induces an increased lattice thermal conductivity, we use the foundation composition of Ge_1.04Te for optimization. Based on the small electronegativity difference between Sb and Ge and the correspondingly high substitution limit, Sb doping is designed to tune the carrier concentration closer to the optimal level with the highest power factor. In the end, an enhanced figure of merit of 1.7 at 723 K can be achieved in Ge_0.96Sb_0.08Te. This study indicates that the stepwise design can optimize the carrier concentration of GeTe-based thermoelectric materials more effectively contributing to high figure of merit.