The morphology of CdS thin films deposited on SnO2-coated glass substrates [for solar cells]

The morphology and microstructure of cadmium sulfide (CdS) thin films are a major concern in the fabrication process of CdTe solar cells. In this work, we investigate the morphology and microstructure of chemical-bath-deposited CdS in order to better understand the growth conditions that give rise to films for optimum device performance. The film morphology was investigated by field-emission, high-resolution scanning electron microscopy (SEM). The film microstructure was studied by transmission electron microscopy (TEM), while the film´s chemistry was investigated by Auger electron spectroscopy (AES). All films examined exhibited pinholes and discontinuities varying in size and density. This may have a significant impact on cell performance by providing shunt paths between the CdTe and the SnO₂. Additionally, the CdS films are heavily faulted, which may partially explain why a high density of planar defects is observed in the CdTe/CdS interface region