In this work we study the electronic passivation of crystalline silicon surfaces with thin silicon films deposited by hot-wire chemical vapour deposition. Both intrinsic hydrogenated amorphous silicon and p-doped nanocrystalline silicon films were evaluated on p- and n-type float zone silicon wafers (1-10 /spl Omega//spl middot/cm). The effective surface recombination velocity was measured by the contactless quasi-steady-state photoconductance technique. Heterostructures consisting of a p-doped nanocrystalline silicon layer with a 10 nm thick intrinsic amorphous silicon buffer allowed effective surface recombination velocities of 120 and 170 cm/spl middot/s/sup -1/ on p- and n-type crystalline silicon. Current density-voltage characteristics of rectifying heterojunctions were also measured. These studies are of great interest to evaluate the possibility to obtain high efficiency heterojunction solar cells fully processed at low temperatures.