Comparative study of ZnS thin films deposited by CBD and ALD as a buffer layer for CIGS solar cell

Alternative deposition methods and materials are of interest for the fabrication of thin film solar cells since they offer potential enhancements for either low cost, high speed or high efficiency but also because they can help in better understanding the underlying physical and chemical processes that could lead to the next generation of solar cells. Structural and optical properties of ZnS and CdS films deposited by either chemical bath deposition (CBD) or atomic layer deposition (ALD) were studied. More specifically, ex-situ measurements by spectroscopic ellipsometry as well as transmission and reflection measurements were performed, allowing for the analysis of the growth processes as a function of deposition parameters. These measurements also allowed for a parameterization of the dielectric functions of ZnS and the evolution of its grain size and band gap as a function of thickness.