%0 Journal Article %A Juan Li %A Xinyue Zhang %A Zhiwei Chen %A Siqi Lin %A Wen Li %A Jiahong Shen %A Ian T Witting %A Alireza Faghaninia %A Yue Chen %A Anubhav Jain %A Lidong Chen %A G. G Jeffrey Snyder %A Yanzhong Pei %B Joule %D 2018 %G eng %N 5 %P 976 - 987 %R 10.1016/j.joule.2018.02.016 %T Low-Symmetry Rhombohedral GeTe Thermoelectrics %V 2 %8 05/2018 %! Joule %X
Thermoelectric materials enable a heat flow to be directly converted to a flow of charge carriers for generating electricity. The crystal structure symmetry is one of the most fundamental parameters determining the properties of a crystalline material including thermoelectrics. The common belief currently held is that high-symmetry materials are usually good for thermoelectrics, leading to great efforts having historically been focused on GeTe alloys in a high-symmetry cubic structure. Here we show a slight reduction of crystal structure symmetry of GeTe alloys from cubic to rhombohedral, enabling a rearrangement in electronic bands for more transporting channels of charge carriers and many imperfections for more blocking centers of heat-energy carriers (phonons). This leads to the discovery of rhombohedral GeTe alloys as the most efficient thermoelectric materials to date, opening new possibilities for low-symmetry thermoelectric materials.