Methodology for ternary Cd<inf>x</inf>Zn<inf>1−x</inf>S deposition by chemical bath

Abstract

Deposition of semiconductor materials by the chemical bath technique has impulsed to reconsider the production of solar cells at industrial scale. The simplicity and low cost of this deposition technique makes it attractive for thin film solar cells production. The CdS and ZnS semiconductors are extensively studied by this technique due to their optical properties as filter or anti-reflective layers. While the band gap energy of CdS is 2.42 eV, ZnS reports a value of 3.70 eV. A technological challenge is to prepare a ternary CdxZn1-xS material that allows us to tune the band gap energy between 2.42 and 3.70 eV, by controlling the x concentration using the chemical bath technique. This work presents two methodologies for preparing this ternary material as a thin layer. For deposition, the chemical bath consists of ZnCl2, SC(NH2)2, and CdCl2 chemical reagents as carriers of ions (Cd2+, Zn2+ and S2-); NH4NO3 as complexing agent, and KOH for pH control. The methodologies for films preparation and their optical, morphological, and structural properties are discussed. XRD analysis shows that ternary material is composed of Zn, Cd and S in a hexagonal structure oriented in the (111) preferential with a mean band gap energy value of 2.50 eV. SEM images on samples show nanoflowers formation. The atomic concentrations of Zn, Cd and S as obtained with EDS and XPS techniques confirm the ternary material formation.