We have studied microcrystalline silicon films (mu c-Si:H:F) deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) at low temperature (similar to 200 degrees C) from SiF4, H-2 and Ar gas mixtures. We found that the H-2/SiF4 ratio plays an important role on the crystalline fraction of the films, specifically on the films grain size, deduced from UV-vis spectroscopic ellipsometry. We observed that higher crystallinity (and larger fraction of large-grains) in the films provides a higher absorption on the infrared (IR) region, which is of particular interest for tandem solar cells. PIN solar cells were fabricated with intrinsic mu c-Si:H:F films of different crystallinity (and different fraction of large grains) in order to observe their effect on the solar cells IR absorption and on the cells performance characteristics. (C) 2011 Elsevier B.V. All rights reserved.