The effects of the CuxS stoichiometry, 1 <= x <= 2, on the optical, electrical, and solar thermal properties of copper sulphide thin films, which have been deposited by chemical spray pyrolysis onto glass, have been studied. A full 3(2) factorial design has been applied to determine the effects of the substrate temperature and deposition time on the electrical and optical properties of the sulphide thin films. The sulphide film properties are strongly related to the CuxS stoichiometry, and this relationship is dependent on the substrate temperature. Therefore, the electrical resistivity of the films varies in the range of 10(-4) Omega cm to 10(-1) Omega cm as x increases from 1 to 2. The relationship between the stoichiometry and conductivity has been established with infrared reflectance, solar absorptance and thermal emittance. The optical constants have been obtained using optical models (Classical Drude). (C) 2014 Elsevier B.V. All rights reserved.