Studies have been carried out on a-Si:H materials and corresponding solar cells fabricated with and without hydrogen dilution of silane by rf PECVD. The effect of hydrogen dilution on the growth kinetics and microstructures and their dependence on the substrate temperature have been studied. Hydrogen diluted a-Si:H materials and solar cells exhibit improved properties and higher stability to light induced changes. Distinct differences are found in the electron mobility lifetime (μτ) products and subgap absorption over a wide range of generation rates. Striking differences are also found in the kinetics of light induced degradation in both the materials and their corresponding solar cells. Direct correlations are presented between the degradation kinetics of p(a-SiC:H)/i(a-Si:H)/n(μc-Si) solar cells and those of thin film materials constituting the i-layers.