Optical Parameters of Nanocrystalline SnO2:F Thin Films Prepared by the Spray Pyrolysis Method

Abstract

SnO2 thin films are usually used as fore contacts in superstrate thin film solar cells such as thin film CdS/CdTe solar cells. Doping SnO2 with fluorine improves its electrical properties and increases its optical bandgap energy besides improving other optical parameters. SnO2:F thin films of thickness around 200 nm were deposited on glass substrates by the spray pyrolysis method at a substrate temperature Ts = 480°C. X-ray diffraction and scanning electron microscopy showed that the films are nanocrystalline. The transmittance of the films was measured at room temperature in the wavelength range 290–1100 nm, and used to calculate the reflectance, which was in turn used to deduce the optical parameters, such as the extinction coefficient, refractive index, real and imaginary parts of the dielectric constant, and energy loss. The relationships between these parameters and photon energy were investigated and compared with the results obtained by other authors.