Se substitution and micro-nano-scale porosity enhancing thermoelectric Cu2Te**Project supported by the National Natural Science Foundation of China (Grant Nos. 51771126 and 11774247), the Youth Foundation of Science and Technology Department of Sichuan Province, China (Grant No. 2016JQ0051), Sichuan University Outstanding Young Scholars Research Funding (Grant No. 2015SCU04A20), the World First-Class University Construction Funding, and the Fundamental and Frontier Research Project

Abstract

Binary Cu-based chalcogenide thermoelectric materials have attracted a great deal of attention due to their outstanding physical properties and fascinating phase sequence. However, the relatively low figure of merit zT restricts their practical applications in power generation. A general approach to enhancing zT value is to produce nanostructured grains, while one disadvantage of such a method is the expansion of grain size in heating-up process. Here, we report a prominent improvement of zT in Cu2Te0.2Se0.8, which is several times larger than that of the matrix. This significant enhancement in thermoelectric performance is attributed to the formation of abundant porosity via cold press. These pores with nano- to micrometer size can manipulate phonon transport simultaneously, resulting in an apparent suppression of thermal conductivity. Moreover, the Se substitution triggers a rapid promotion of power factor, which compensates for the reduction of electrical properties due to carriers scattering by pores. Our strategy of porosity engineering by phonon scattering can also be highly applicable in enhancing the performances of other thermoelectric systems.