Realization of High Thermoelectric Figure of Merit in GeTe by Complementary Co-doping of Bi and In

Abstract

Thermoelectric (TE) materials are expected to play a prime role in future energy utilization and management. Pb-based materials have proven to be champion TE materials for mid-temperature power generation. However, the field demands Pb-free materials with high TE figure of merit (zT) along with high TE power conversion efficiency (η). Recently, GeTe has emerged as a potential alternative of PbTe. However, the low Seebeck coefficient and high thermal conductivity of GeTe are the two principle constraints in the way of optimizing its zT. Here, we have demonstrated a distinct but complementary role of In and Bi doping in GeTe in modulating the electronic structure and reducing the lattice thermal conductivity. These synergistic effects resulted in a high zT of ∼2.1 at 723 K and an extremely high η of ∼12.3% in single-leg TE generator for the temperature difference of 445 K in In and Bi co-doped GeTe. This co-doping approach with synergistic effects paves the way for the new generation of GeTe thermoelectrics.