Improved thermoelectric performance of GeTe via efficient yttrium doping

Optimization of the carrier concentration by doping/alloying is a key prerequisite for improving thermoelectric performance. In reality, it is, however, challenging to identify effective dopants in some specific systems. Herein, we discovered that Y doping significantly reduced the carrier concentration, enhanced the power factor, and, therefore, boosted thermoelectric performance. The high Y-doping efficiency had origin in the fact that the compensating effect due to Ge vacancies was weaker in comparison to other dopants in GeTe because the slightly increased rhombohedral interaxial angle suggested that the Ge-vacancy concentration would not be altered dramatically. In addition, first-principles calculations revealed that Y doping did not induce significant modifications on the band structure, consistent with electrical transport measurement results. Moreover, Bi doping was found to be more powerful than Sb doping to further increase electrical resistivity and to enhance performance in which the highest peak ZT similar to 1.8 together with a high average ZT similar to 1.1 from 300K to 723K was achieved. Our work not only highlighted the efficacy of Y doping in enhancing the thermoelectric performance of the GeTe system but also developed advanced GeTe-based materials for power generation applications.