Realizing Excellent Thermoelectric Performance in Band-Converged GeTe-based Materials by Entropy and Vacancy...

Entropy engineering has emerged as an effective strategy for optimizing thermoelectric performance by decoupling electrical and thermal transport properties. By co-tuning the electronic band structure and phonon scattering mechanisms based on entropy and vacancy engineering, a high zT value of 2.62 at 700 K was achieved in GeTe-based materials. First, doping interstitial Cu atoms in Pb and Bi doped GeTe matrix has increased the carrier mobility and electrical properties by reducing the intrinsic Ge vacancies. Subsequently, introducing Sb at Ge sites will increase the average lattice symmetry based on entropy stabilized crystal structure, promoting the band convergence and the Seebeck coefficient due to the increased effective mass of density of states. The tuned Ge vacancies based on changing Sb content increased the electronic density of states, effectively suppressing the bipolar effect and achieving high power factor at the whole temperature range. Therefore, based on the entropy and vacancy co-tuning strategy, a high average zT of 1.8, along with a high experimental conversion efficiency of 13% with the fabricated segmented module were realized. This work provides an entropy and vacancy co-tuning strategy to systematically optimize the performance of thermoelectric power generation in a wide temperature range.