The effects of post-treatments on the photovoltaic properties of spray-deposited SnO2:F thin films

Polycrystalline and highly transparent SnO2:F thin films were prepared by the spray pyrolysis (SP) technique at a substrate temperature Ts = 480 °C. The effects of annealing in nitrogen atmosphere at T = 400 °C and etching by HNO3 in distilled water on the photovoltaic properties of the films were investigated. The electrical properties were studied by recording the I-V plots which were used to find the resistivity. The structural properties of the films were investigated by determining the X-ray diffraction (XRD) patterns, and observing the scanning electron microscope (SEM) images. The effects of this treatment on the optical properties of the films were investigated by recording the transmittance curves and estimating the bandgap energy of the films. It was found that annealing in nitrogen atmosphere decreases the resistivity, increases the grain size and slightly decreases the transmittance of the films. On the other hand, etching followed by annealing results in more decrease in the resistivity, enhances the crystal growth, slightly increases the bandgap and results in more oriented and larger grain size.