Dependence of solar selectivity of copper-black films on their structure, chemical composition and morphology

Abstract

The composition and morphology of anodically grown solar-selective copper-black films have been investigated using X-ray photoelectron spectroscopy with depth profiling, scanning electron microscopy and X-ray diffraction. It has been found that the films showing the best selectivity have their top layer consisting predominantly of crystalline cupric oxide (CuO). In the underlying region the dominating phase is cuprous oxide (Cu₂O) with Cu/O ratio increasing systematically towards the copper substrate. It is shown that the enhanced absorption in the solar region of the spectrum is due to the stacking of layers with graded composition and also due to the surface morphology of the film.