Effect of the stoichiometry of CuxS thin films on the optical and electrical properties and the solar thermal performance

•The effect of spray parameters on the CuxS has been found by 32 factorial designs.•When obtained at lower temperatures, CuxS is conductive and show low-e behaviour.•CuxS (1.8 ≤x≤2) stoichiometric films were obtained at higher temperature.•The relationship between optical constants and stoichiometry has been determined.•The relationship between the electrical conductivity and solar parameters is shown.

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 32 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 Ω cm to 10−1 Ω cm as × 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).