Thickness Dependence of the Optical Parameters of Spray-Deposited SnO2:F Thin Films

Tin oxide is a transparent conductive oxide with potential use in heterojunction thin film solar cells such as CdS/CdTe solar cell as a fore contact, and in optoelectronic devices. These applications require a deep understanding of the optical properties of the material and optimization of its optical parameters. Fluorine doping of the films increases their conductivity, which is important for high cell performance. In this work fluorine doped tin oxide (SnO₂:F) thin films were prepared by the spray pyrolysis (SP) technique on glass substrates. The films were found to be polycrystalline as seen in the scanning electron microscope (SEM) images. The transmittance spectra of the films were measured at room temperature and used to deduce the optical parameters such as the direct and indirect optical bandgap energies, Urbuch tail width, extinction coefficient, and refractive index. The dependence of these parameters on film thickness was investigated.