Systematic study into the synthesis and shape development in colloidal CuIn_xGa_{1- x}S₂ nanocrystals

Herein, we report a systematic study on the colloidal growth of CuIn _xGa_1-xS₂ nanocrystals and nanorods. The formation of CuIn_xGa_1-xS₂ nanocrystals is shown to occur in several discrete steps, beginning with formation of the binary copper sulfide, transitioning through ternary and subsequently progressing to yield the quaternary form. This allows fine-tuning of the aspect ratio through incorporation of amine ligands of differing alkyl chain length giving nanorods ranging from ∼7.5 to 14 nm in diameter. The complexity of this system is extensively detailed with a sequential investigation of the effect of amines, thiols, phosphonic acids, in addition to coordinating and noncoordinating solvents on growth protocols. A diverse range of shape morphologies is attained, ranging from hexagon discs to hatchet shaped crystals, with an optimal synthetic window demonstrated using thiol-amine ligands to generate regular nanorods of controlled dimensions. These nanorods can be assembled over large-scale areas with each nanorod vertically aligned and close packed, allowing for device scale properties defined by the aspect ratio of each building block.