Off-stoichiometry effect on thermoelectric properties of the new p-type sulfides compounds Cu2CoGeS4

An in-depth analysis of Cu2+xCo1-xGeS4 (CCGS) has been performed to illustrate its potential as a new p-type compound for thermoelectric (TE) applications with suitable thermal stability. An intrinsic semiconductor behavior is reported with attractive TE properties, characterized by a large Seebeck coefficient and intrinsic low thermal conductivity. Band structures and elastic properties calculations sustained the experimental observations and revealed the dominant role of Cu/Co ratio in electrical transport properties. A promising TE performance is achieved through a carrier concentration tuning by Cu/Co ratio control, with a zT = 0.37 at 725 K resulting from combined large PF enhancement and a reduced kappa. (C) 2020 Elsevier B.V. All rights reserved.