The design of an antireflective filter using TiO$_2$--ZnO and TiO$_2$ thin films

In the present work, we designed an antireflective filter for the visible region composed of TiO$_2$ and ZnO--TiO$_2$ thin films. Initially, single layers of the films were coated on both sides of the substrate using the sol-gel spin coating method. UV--visible spectroscopy was used to measure the transmittance and reflectance of the films. The thicknesses, refractive indices and extinction coefficients were determined by fitting to a modified Tauc-Lorentz model. Having determined the appropriate film thicknesses and refractive indices needed for an antireflective filter in the desired wavelength region, the single layers were combined to build the filter. The theoretical model of Ref.[1], which accounts for the densification occurring during the construction of the multilayer stack, was adapted to extract the optical properties of the individual layers in the stack, which were then compared to the single layer results. [1] D. Saygin Hinczewski, M. Hinczewski, F.Z. Tepehan and G.G. Tepehan, Solar Energy Materials and Solar Cells 87, 181 (2005).