A low cost spin coating route of fabricating CuInS2
polycrystalline thin films by reactive sin-tering method was put forward. The ink for spin coating was optimized by pre-reducing the precursor powders in hydrogen, which turned the nanoparticle precursor powders from mixed sulfides into a mixture of CuInS2
and Cu-In metal alloys. The results of scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and Raman spectra showed that this optimization could highly improve the performance of CuInS2
polycrystalline thin films, including higher packing density, less impurity phases, and better quality. The en-ergy gap of optimized CuInS2
thin film was determined to be about 1.45 eV by absorption spectroscopy measurement.