Intrinsic defects and the influences on electrical transport properties in quaternary diamond-like compounds:Cd_(2)Cu_(3)In_(3)Te_(8)as an example

Over the years,the fact that the quaternary diamond-like thermoelectric materials show much lower carrier mobilities than ternary compounds remains mysterious.In this work,by adopting first-principles defect chemistry and electrical transport calculations,the fundamental origin of the difference on carrier mobility between quaternary and ternary diamond-like compounds is addressed,exemplified by Cd_(2)Cu_(3)In_(3)Te_(8).The results of defect chemistry show that the main intrinsic defects in quaternary compound Cd_(2)Cu_(3)In_(3)Te_(8) are substitutional defects,i.e.,CdIn and CdCu,differing from the copper vacancy defect in ternary Cu-based compound such as CuInTe_(2).The low defect formation energies in Cd_(2)Cu_(3)In_(3)Te_(8) result in high defect concentrations,which is caused by the similar atomic radii and electronegativities between CdeIn and CdeCu.Further calculations show that the low-energy defects are mainly located around the valence band maximum in Cd_(2)Cu_(3)In_(3)Te_(8).The electrical transport calculations,considering both the acoustic phonon scattering and ionized impurity scattering,demonstrate that mainly due to the higher concentration of the ionized defects,the mobility of the quaternary Cd_(2)Cu_(3)In_(3)Te_(8) is much lower than that of ternary CuInTe2.Our work sheds light on the intrinsic defects in quaternary diamond-like compounds and their influence on charge transport.