R.f. sputtering of high-quality Cu/In precursor layers and conversion to CuInS2 using elemental sulfidization processes

Abstract

Thin films of CuInS2 have been produced by a two-stage process, the formation of a Cu/In precursor layer using r.f. magnetron sputtering of alternate layers of the elements followed by the conversion into the compound by either (i) annealing the precursor layers in a closed chamber in the presence of sulfur or (ii) annealing the precursor layers in sulfur that was transported over the layers using argon as a carrier gas. These out-of-line-of-sight methods have potential for large-scale “batch processing” of the absorber layers. The physical and chemical properties of the precursor layers and the CuInS2 formed were investigated using a range of methods including energy dispersive X-ray analysis, Rutherford backscattering spectrometry, and synchrotron X-ray diffraction. The data confirms that the uniform layers produced using the former method have potential for use in both substrate and superstrate configuration devices. For the latter method there was significant indium loss during the conversion process and this problem needs to be overcome before the layers can be used in solar-cell devices.