Modular nanostructures advance highly effective GeTe thermoelectrics

Abstract

Here, we demonstrate that the electronic band structure of GeTe can be finely modified by orbital interaction manipulation. Bi-Cd-I codoping lowers the valance band maximum position and decreases the energy offset through weakening cation-s and anion-p orbital interactions, promoting strong band convergence in cubic GeTe. The dramatic enhancement of the Seebeck coefficient induces a high and almost stable power factor over a very wide temperature range. The formation of modular nanostructures within the matrix plays a dominant role in reducing the lattice thermal conductivity, leading to an ultralow lattice thermal conductivity. Resultantly, a maximum zT of 2.5 was achieved in GeTe-based thermoelectric materials. Notably, the material achieves a broad plateau of zT > 2.4 for a wide temperature range from 623 K to 823 K, resulting a record high average zT of 1.82. The exceptional thermoelectric performance leading to an outstanding power generation efficiency of ∼12 % in a single leg. Such outstanding thermoelectric performance is attained by the synergistic effects of modular nanostructures and orbital interaction manipulation, opening up a great opportunity for advancing thermoelectrics.