Al ₂O ₃/TiO ₂ thin films were deposited onto monocrystalline silicon surfaces using an atomic layer deposition. Their surface morphology and optical properties were examined for their possible use in solar cells. The surface condition and chemical composition were characterized using a scanning electron microscope and the thickness was measured using a spectroscopic reflectometer. The refractive index and the reflection characteristics were determined. First, the optical properties of the Al ₂O ₃ thin film and its influence on recombination in the semiconductor were examined. In this way, it can fulfil a double role in a solar cell. Since reflection reduction was only achieved in a narrow range, it was decided to use the Al ₂O ₃/TiO ₂ system. Thanks to this solution, the light reflection was reduced in a wide range (even below 0.2%).