Surface morphologies of spectrally selective and polarization-dependent angular optical reflectors of SnOx:F-coated anodized aluminum

In this paper, we present the optical properties of spectrally selective reflector surfaces of pyrolytically deposited fluorine doped tin oxide (SnOx:F) on pre-anodized aluminum. The aim is to obtain a high solar reflectance for wavelengths below 1.1 μm and low solar reflectance for wavelengths above 1.1 μm referred to as Rcell and Rtherm, respectively. Thin SnOx:F films were grown on pre-anodized aluminum by spray pyrolysis, while the anodic layers were prepared on aluminum electrochemically using a non-stirred H2SO4 bath. The presence of a thin, 100–200 nm thick, interfacial anodic (Al2O3) layer is shown to have a strong influence on the optical selective reflectance properties. X-ray diffraction and scanning electron microscopy have been used to characterize both the anodic and tin oxide films. A good contrast between Rcell and Rtherm has been achieved, with Rcell and Rtherm having values of 0.80 and 0.42, respectively.