One-step synthesis of CuInS₂ nanoparticles using aqueous chelated metal complexes as a starting material

Thin film compound semiconductor solar cells, including copper indium sulfide (CIS), have potential as next-generation power supply sources. However, recent fabrication processes include gas phase reactions, which consume much energy and generate abundant loss of material resources. Therefore, the development of alternative eco-friendly methods without a gas phase reaction has been actively researched. Herein, we synthesize CIS nanoparticles via a liquid phase reaction using iminodiacetic acid (IDA) and glycine (Gly) as the complex reagent to homogenize copper and indium complexes. The X-ray diffraction (XRD) profiles of the as-synthesized nanoparticles in a buffer solution exhibit broad peaks, which nearly correspond to CIS. These peaks grow sharply after annealing. Selected area electron diffraction and high-resolution transmission electron microscopies indicate the presence of the (112) phase of CIS but the crystallinity of our CIS with IDA and Gly differs. The results indicate that maintaining a homogenized condition of metal complexes by pH stabilization using a buffer solution might be maybe important for aqueous synthesis of CIS.