This work deals with the study of the role of intra-gap density of states and films composition on the colour selection of the collection spectrum of glass/ITO/a-Si-x:C1-x:H/A1 Schottky photodiodes produced in a conventional plasma-enhanced chemical vapour deposition (PECVD) system using as gas sources silane and a controlled mixtures of silane and methane. To do so, properties of the films were investigated, especially the one concerning the determination of the valence controllability C of the films produced and the density of bulk states. Besides that, a PINIP device was also produced, using the a-Si-x:C1-x:layer that lead to the best Schottky diode performances.