Optical and solar selective properties of chemically sprayed copper sulphide films

Abstract
The present study deals with the optical properties of copper sulphide films obtained by the spray pyrolysis technique. Films deposited at 250 degrees C substrate temperature have Cu2S chalcocite as the dominant phase. The films are stable and have good adhesive properties. Optical constants of the films are calculated from the measured reflectance, transmittance and thickness data using the iteration method. The films have an indirect band gap of 1.0 and a direct band gap of 1.9 eV. Films deposited on aluminium substrates work as solar selective absorbers of the semiconductor/metal tandem type with maximum solar absorption ( alpha s) of 0.89 and minimum thermal emittance ( epsilon T) of 0.25.