CuInS2 thin films were prepared by sulfurization of sequentially deposited Cu/In stacks with elemental sulfur. Precursors as well as reacted films are characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD). Excess copper is required for optimum properties and leads to a CuS secondary phase segregated at the surface. Stoichiometry is regained by etching after which heterojunctions are formed by deposition of a CdS/ZnO window layer. An active area efficiency of 10.4% has been achieved.