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

Abstract

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 ${\mathrm{CuInTe}}_2$ comprise a large range of compositions in the pseudobinary system ${\left({\mathrm{Cu}}_2\mathrm{Te}\right)}_x{\left({\mathrm{In}}_2{\mathrm{Te}}_3\right)}_{1-x}$, 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 ${\mathrm{Cu}}_2\mathrm{Te}$-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 ${[{\mathrm{Cu}}_{\text{In}}^{2-}·2{\mathrm{Cu}}_i^{+}]}^0$ in chalcopyrite ${\mathrm{CuInTe}}_2$.