Inorganic ligand mediated synthesis of CuInS2nanocrystals with tunable properties

Abstract

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)₂Cl₂] as an auxiliary agent (capping agent and shape-control agent). Factors including reaction temperature, reaction time and amount of Sn(acac)₂Cl₂, 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)₂Cl₂ played an important role in the formation of the final nanocrystals. Sn(acac)₂Cl₂ 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 ∼5 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)₂Cl₂ and has been compared with the mechanism of CuInS₂ NCs prepared without the participation of Sn(acac)₂Cl₂. 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.