We show results of structural, chemical and optoelectronic characterizations to polymorph silicon thin films (pm-Si:H) grown in PECVD system using dichlorosilane as precursor gas. We have examined the effects of pressures and hydrogen dilutions on chemical and structural characteristics of pm-Si:H, and how these characteristics influence on the optoelectronic and photodegradation properties of the material. By Raman spectroscopy, the nano-structural character of material was determined in terms of average size and crystalline fraction. With UV-VIS the optical gap of each film was determined, finding that this value is modified according to nano-structural characteristics of this material. By XPS, incorporation of oxygen in the samples with largest nanoclusters, was found. With FTIR, bond configurations associated to photo-stability of the material were found, which was confirmed by measuring photoconductivity, through prolonged intensities of light soaking of 94 mW/cm2 at controlled temperature, finding greater photo-stability in the samples where Oxygen was found. The results show the importance of the role of chlorine atoms in the photo-stability of pm-Si: H, an important key to optimize its optoelectronic properties and implement it in manufacture solar cells.