Augmented chalcopyrites: A search for new Cu-In-Te phases

Chalcopyrites are ternary crystalline compounds which have found use in a diverse array of applications, from solar cells to thermoelectric devices. These are known to be ternary-compound analogs to diamond or sphalerite. "Defect chalcopyrites,"which are chalcopyrite structures stabilized with ordered vacancies and substitutions, are well attested and can serve as a method of tuning material properties through control of stoichiometry. In particular, defect chalcopyrites related to the thermoelectric compound CuInTe2 comprise a large range of compositions in the pseudobinary system (Cu2Te)x(In2Te3)1-x, where x<0.5. In contrast, the converse case of "augmented chalcopyrites,"namely, x>0.5, is much less known or studied. We report the discovery of a range of Cu2Te-rich compositions in this binary system where stable phases can potentially be found. Here, the stoichometry of augmented chalcopyrites is likely to be modulated by the concentration of defect clusters [CuIn2-·2Cui+]0 in chalcopyrite CuInTe2.