This work presents results concerning the development of n + - ZnO/i-ZnO and n + - ZnO/ZnSe bilayer structures with adequate properties to be used as optical windows in solar cells based on CuInSe 2 thin films. The optical and morphological properties of each of the layers constituting the bilayer structures were studied through spectral transmittance and atomic force microscopy (AFM) measurements. The studies revealed that windows of this type allow a significant increase of the spectral range of absorbed radiation by the solar cell in comparison with those using ZnO/CdS as optical window.