The electrical and structural properties of n-type mu c-Si films prepared by Cat-CVD with different doping ratios R = PH3/SiH4, deposition pressures P-g, hydrogen dilution ratios S-H, and filament temperatures T-f have been characterized by dark conductivity, Raman Scattering and Photothermal Deflection Spectroscopy (PDS) measurements. The crystalline volume fraction (X-c) of n-type mu c-Si:H films is sensitive to T-f rather than S-H and R. The density of states in n-type mu c-Si:H films were investigated by PDS. The heterojunction solar cells of n-type mu c-Si:H on p-type c-Si (100) with an undoped a-Si:H buffer layer were performed at a deposition rate of 0.35 nm/s. The best J-V parameters of solar cell are J(sc) = 29.5 mAcm(-2), V-oc = 483 mV, FF = 70%, and q = 10.2%. (c) 2005 Published by Elsevier B.V.