The authors developed the RF plasma enhanced chemical vapour deposition method for preparation of a-Si:C:H films of potential optoelectronic properties. The films were obtained on glass and (001) Si in optimised technological parameters such as content of gaseous mixture of SiH4, and CH4, gas pressure, temperature and RF power density. The surface morphology, chemical composition, optical properties, chemical bonding structure, were investigated. The film structure and composition depended on process parameters and configuration. The results of optical investigations show that these materials are characterised by variable optical gap dependent on carbon content. In chosen conditions it is possible to produce material of optimal optical properties for solar application as antireflective and protective coatings for solar cells. (C) 2004 Published by Elsevier B.V.