Spinel Indium Sulfide Precursor for the Phase-Selective Synthesis of Cu-In-S Nanocrystals with Zinc-Blende, Wurtzite, and Spinel Structures

Group I-III-VI ternary chalcogenides have attracted extensive attention as important functional semiconductors. Among them, Cu-In-S compounds have seen strong research interest due to their potential applications in high-efficiency solar cells. However, the controllable synthesis of Cu-In-S nanostructures with different phases is always difficult. In this research, zinc-blende CuInS2, wurtzite CuInS2, and spinel CuIn5S8 could be selectively synthesized using spinel In3-xS4 as the precursor by a simple solvothermal method. X-ray powder diffraction was used to determine the phase and crystal structure, and transmission electron microscopy was employed to characterize the morphologies of the as-prepared samples. Experiments showed that the acidity-basicity of the reaction system and the coordination and reducibility of the capping ligands were crucial to the final phases of the products. The UV-vis-NIR spectra of the three phases all exhibited a broad-band absorption over the entire visible light and extending into the near-infrared region, and the zinc-blende, wurtzite, and spine! Cu-In-S nanocrystals showed band gaps of 1.55, 1.54, and 1.51 eV, respectively, which indicates their potential applications in thin-film solar cells.