Glass/ZnO:Al/p (SixC1-x: H)/i (Si:H)/n (SixC1-x: H)/Al (0 < x < 1) heterojunctions were produced by PE-CVD at low temperature. Junction properties, carrier transport and photogeneration are investigated from illuminated current- and capacitance-voltage characteristics and spectral response measurements, in dark and under different illumination conditions. For the heterojunction high series resistance around 10(6) Omega and atypical J-V characteristics are observed leading to poor fill factors. It was also observed that the responsivity decreases with the increase of the light bias intensity. For the homojunction, the behaviour is typical of a non-optimised p-i-n cell and the responsivity has a slight variation with the light bias conditions. A numerical simulation gives insight into the transport mechanism suggesting that the potential drop across the low-conductive a-SiC:H contact causes a significant change in the drift-diffusion balance inside the i-layer bulk. In the homojunction even at high light fluxes the transport process remains drift dominated.