The electrical and optical properties of n-doped polycrystalline 3C-SiC films grown on 6 inches Si wafers have been investigated as a function of precursor gases, deposition temperature and C/Si ratio. The Si/SiC interface has been optimized, eliminating the voids formation through a double temperature step process and by introducing a thin not intentionally doped layer. Films with high surface roughness, favourable for light trapping in photovoltaic applications, and with resistivity around 20 mOhm cm have been obtained for C/Si ratio close to 1. Simple solar cells have been also manufactured and proved the functionality of poly 3C-SiC/Si heterojunction solar cell. Increased quantum efficiency in the range 300-500 nm has been observed, compared to amorphous Si, making poly 3C-SiC heterojunction solar cells interesting for high temperature applications or water splitting.