Impact of different thermal treatments on ZnS physical properties and their performance in CdTe solar cells

The n-type CdS is commonly used as a window layer on photovoltaic solar cells, but CdS has disadvantages such as a direct band gap of 2.4 eV that reduces the photons collection in the UV range. As an alternative solution, ZnS (with a band gap value between 3.6 eV and 3.9 eV) thin film was implemented in the photovoltaic devices as a buffer layer to try to solve the problem. ZnS thin films were grown by chemical bath deposition (CBD) technique and thermally treated on Air, Argon, Oxygen and CdCl2 atmospheres to improve their optoelectronic properties. CdCl2 treatment formed a ZnxCd1−xS ternary compound. In this work, physical properties of ZnS thin films as deposited and thermally treated were studied; on the other hand, ZnS/CdS and ZnxCd1−xS/CdS junctions are implemented in CdTe solar. Experimental and simulated I–V curves were fitted and analyzed.