Colloidal Cu₂ZnSn(SSe)₄ (CZTSSe) Nanocrystals: Shape and Crystal Phase Control to Form Dots, Arrows, Ellipsoids, and Rods

Herein, we report shape control in the CZTSSe nanocrystal system by tuning the occurrence of polytypism between wurtzite and zinc-blende phases. We have isolated the key control factors in this system and show that the choice of solvents/surfactants and precursors and how they are introduced can allow shape control from dots to ellipsoids to arrows and rods. The shape evolution is dictated by independently controlling the respective growth rates of either the zinc-blende or wurtzite regions in the polytypic system. We further show the extension of this synthetic control to eliminate polytypism while retaining anisotropy allowing for single-phase wurtzite nanorods of CZTSSe.