A p-a-Si:H layer, deposited by a photo-assisted chemical vapor deposition (photo-CVD) method, was adopted as the window layer of a hydrogenated microcrystalline silicon (pc-Si:H) solar cell instead of the conventional p-pc-Si:H layer. We verified the usefulness of p-a-Si:H for the p-layer of the mu c-Si:H solar cell by applying it to SnO2-coated glass substrate. It was found that the quantum efficiency (QE) characteristics and solar cell performance strongly depend on the p-a-Si:H layer thicknesses. We applied boron-doped nanocrystalline silion (nc-Si:H) p/i buffer layers to mu c-Si:H solar cells and investigated the correlation of the p/i buffer layer B2H6 now rate and solar cell performance. When the B2H6 flow rate was 0.2 sccm, there was a little improvement in fill factor (FF), but the other parameters became poor as the B2H6; flow rate increased. This is because the conductivity of the buffer layer decreases as the B2H6 flow rate increases above appropriate values. A mu c-Si:H single-junction solar cell with ZnC/Ag back reflector with an efficiency of 7.76% has been prepared. (C) 2008 Elsevier B.V. All rights reserved.