Spray deposited thin films of SnO2: F/CdS: In bilayers produced using different fluorine sources: NH4F and HF

Abstract

Thin films SnO2: F/CdS: In bilayers were prepared using the spray pyrolysis method on glass substrates at a substrate temperature Ts = 450 °C. Ammonium fluoride (NH4F) and hydrofluoric acid (HF) were both used as the fluorine sources in the precursor solution of SnO2: F. Properties of the two types of bilayers obtained using the two fluorine sources were investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmittance measurements (UV-Vis) were used to characterize the films. It is found that the bilayers prepared using HF as a source of fluorine have more ordered crystal growth, and sharper absorption edge. From the inspection of the first derivative of the absorbance it is expected that more interdiffusion on the SnO2: F/CdS: In interface takes place in the bilayers produced using HF. These results confirm that these bilayers are better as fore contacts for thin film CdS/CdTe solar cells.