Controlled synthesis of wurtzite CuInS₂ nanocrystals and their side-by-side nanorod assemblies

Wurtzite CuInS₂ nanocrystals have been synthesized by direct reaction of copper nitrate, indium nitrate and dodecanethiol. The size and shape of the nanocrystals could be elaborately controlled by varying the Cu/In ratio and additional ligands other than dodecanethiol, such as oleylamine and oleic acid. Especially, the nanorods obtained under a Cu/In raw material ratio of 2:1 with the assistance of both dodecanethiol and oleic acid have good uniformity. They could further assemble into large-scale superlattices on substrates by solvent evaporation method. On the other hand, the optical property studies of the nanocrystals show that the band gap of wurtzite CuInS₂ is 1.63 eV, which is optimal for solar cell applications. This report provides valuable insight into the controlled synthesis of ternary I-III-VI₂ semiconductors and the assembly process, packing them into oriented films.