Tunable quantum gaps to decouple carrier and phonon transport leading to high-performance thermoelectrics
Yong Yu, Xiao Xu, Yan Wang, Baohai Jia, Shan Huang, Xiao‐Bin Qiang, Bin Zhu, Peijian Lin, Binbin Jiang, Shixuan Liu, Qi Xia, Kefan Pan, Di Wu, Hai‐Zhou Lu, Michel Bosman, Stephen J. Pennycook, Lin Xie, Jiaqing He
Abstract
Thermoelectrics enable direct heat-to-electricity transformation, but their performance has so far been restricted by the closely coupled carrier and phonon transport. Here, we demonstrate that the quantum gaps, a class of planar defects characterized by nano-sized potential wells, can decouple carrier and phonon transport by selectively scattering phonons while allowing carriers to pass effectively. We choose the van der Waals gap in GeTe-based materials as a representative example of the quantum gap to illustrate the decoupling mechanism. The nano-sized potential well of the quantum gap in GeTe-based materials is directly visualized by in situ electron holography. Moreover, a more diffused distribution of quantum gaps results in further reduction of lattice thermal conductivity, which leads to a peak ZT of 2.6 at 673 K and an average ZT of 1.6 (323-723 K) in a GeTe system. The quantum gap can also be engineered into other thermoelectrics, which provides a general method for boosting their thermoelectric performance.