Inorganic ligand mediated synthesis of CuInS2 nanocrystals with tunable properties

In this paper, novel chalcopyrite copper indium sulfide (CuInS2) nanocrystals (NCs) were synthesized by a simple one-pot route using the inorganic ligand [Sn(acac)(2)Cl-2] as an auxiliary agent (capping agent and shape-control agent). Factors including reaction temperature, reaction time and amount of Sn(acac)(2)Cl-2, that influence the morphology, size, monodispersity and optical properties of the CuInS2 NCs were studied in detail. The results showed that the morphology and size of the CuInS2 NCs can be controlled by changing the reaction conditions, and Sn(acac)(2)Cl-2 played an important role in the formation of the final nanocrystals. Sn(acac)(2)Cl-2 not only controlled the shape and improved the monodispersity, but also improved the chemical composition and photoelectric response of the prepared CuInS2 NCs. Time-dependent experiments were performed to observe the growth of CuInS2 NCs. CuInS2 NCs with sizes ranging from similar to 5 to similar to 17 nm could be obtained by adjusting the reaction conditions, and the corresponding optical and electrical properties of the different size CuInS2 NCs were also investigated. The Ostwald ripening mechanism has been proposed for the formation of final polygon CuInS2 NCs with the participation of Sn(acac)(2)Cl-2 and has been compared with the mechanism of CuInS2 NCs prepared without the participation of Sn(acac)(2)Cl-2. CuInS2 NCs synthesized by the proposed method showed broad absorption in the visible region and a high photoelectric response to visible light, which indicates that CuInS2 NCs capped with inorganic ligands may have potential applications as an absorber layer in solar cells. The synthesis strategy developed in this work may be used as a general process for the synthesis of pure or doped chalcogenide NCs.