Optical Properties and Selective Solar Absorption of Composite Material Films.

摘要

Composite material films are widely used as selective solar absorbers. The authors investigated the cermets Au-MgO and W-MgO and the semiconductor-insulator composites Si-CaF2 and Si-MgO prepared by co-sputtering. For Au-MgO the dielectric constant does not exhibit the resonance structure near 0.6 micrometer that is characteristic of other systems of gold particle dispersions, and furthermore the infrared absorption is much larger than that predicted by theory. This anomalous behavior could be due to the textured surface of the films. For the W-MgO films the observed dielectric constants are in good agreement with the Maxwell Garnett theory. In the films with Si dispersions strong absorption bands appear in the infrared; these are due to compounds formed by chemical reaction between Si and the matrix materials. The photothermal conversion efficiency of solar energy of these materials was estimated and compared with other selective solar absorbers. (Author)